Hmmm in terms of power projection, numbers, quality, intelligence gathering abilities, logistics, esprit de corps etc., although they are stretched already and recruitment is dropping I would, like many others, put the US on top, with the best or some of the best equipment in all branches with regular soldiers received very good training. The weakness I see is if in the case of an offensive operation, the sustainability of any US force for long periods of time. At defence, the US is a proverbial fortress from a conventional point of view. Also the quality of the National Guard in terms of training is somewhat troublesome as is the current general morale at home and abroad. The US still has the best air force, best navy (by far) and the best regular, professional army.
Number two is China, while things seem to be getting worse and worse wit Russia sometimes, China seems to be constantly improving. The quality of it's training is increasing, and all branches of the military are benefiting from a massive increase in spending. China still has a growing population that's already extremely large and has one of the most experienced and largest industries in the world which can be seen in the rapid employment of the QBZ-95 as the latest frontline assault rifle. The only problem is China, while having some interesting naval assets, has no real ability to protect any large, requisitioned merchant marine and regular navy force. China's navy right now is focusing on smaller warships that are suited to patrolling and defending China's water and protecting her interests. The Air force is also simply not good enough for a country like China, it doesn't matter how many MiG 21's you have, they're still Mig-21's and are really only effective against other MiG-21's or other 3rd and light 4th generation fighter aircraft. Hopefully the J-13 or J-xx can provide China with something more capable. China's army is shrinking, and that is actually a good thing, a smaller, leaner and more professional army that is focused on fighting high-tech, localised conflicts, can be just as effective as a large, under-equipped army. It's not as if China's military still isn't big, it's massive. In terms of hardware, China is a mixed bag, China's traditional strength, small arms, has been given a massive shot in the arm and the current Chinese small arms arsenal is completely different from the days of the Sino-Vietnamese War. Heavy industry, needs to step up to the plate, the obsolete Type 59 which would be more of liability than an asset, still out numbers all other Chinese tanks combined. China ranks 'pretty good and improving' in all branches.
Number three would be Russia, which is no longer a superpower but still a key player and regional power (which of course, is multiple regions given the size of Russia). Russia has a problem with a plummeting population, they simply cannot sustain a WWII style Eastern front campaign today. The key to Russia is the experience of their forces and the sheer size of Russia means power projection is not terribly difficult because they're more or less close to everyone else already and Russia's mature military and industry means that it can continue to be one of the most influential exporters of military hardware in the world. The current problem with the Russian military is the ridiculous disparity in the quality of her regular conscript army and her specialised soldiers such a her airborne and the disparity of equipment between conscripts and special forces is astounding sometimes. Although Russia's military fortunes are taking a turn under Putin, Chechnya is a constant reminder of Russia's military weakness. Russia can at least boast that it has a pretty modern airforce that is more than capable of holding it's own and the Russian navy, although rusty and under funded has new life with the two naval bases they are re-establishing in Syria and is still pretty large considering most of Russia’s territorial waters are frozen for most of the year.
My number four would be India surprisingly enough. India has an extremely well equipped navy, with 38 more ships currently on the way in various shipyards around the world and in India and is more or less, the sole power in the entire Indian Ocean save for the many US naval bases in Middle East. India's air force is on the very verge of big, massive upgrade with 126 new 4.5 generation fighters from... god knows where, but certainly somewhere and they should be delivered by 2012ish, or in the case of the MiG-35, even sooner. In addition, the LCA project is finally complete the HAL should have a sizeable amount of Tejas light fighters in the air by 2010. India's army on the other hand seems to still be stuck in the 80's and is only now modernising, finally replacing the tried and true Sterling with the not so tried and true mini Tavor TAR-21 (which they call the 'Zittara'). The Indian army needs to seriously re-evaluate it's current Cold War era doctrines, it would certainly pay off. India during the Kargil War of 1999 showed that it's current strength lies with it's special (usually ethnic, Sikhs, Gurkhas etc.) forces. India is quite flexible in that pretty much every environment on Earth can be found in India; forests, jungles, plains, mountains, deserts, islands etc. The gap between Russia and India is far too great currently though. India is over reliant on foreign defence companies and keeping track of so many different weapons and arms systems from all over the world is very difficult. India's military industry is also, still far too young and needs a decade more before it’s finally reached China's level and who knows how much longer to reach Russia's level of technological sophistication (although in terms of electronics, such as those found in the Tejas and LCH project, they're quite advanced)
Fifth is the UK, you would be hard pressed to find anything negative to say about the military of the UK, it's well funded, experienced, well equipped and well researched. It's certainly the best army in Europe (much to the chagrin of the UK's eternal (friendly) rival, France). The UK has shown, even when caught completely by surprised, they still have excellent power projection capabilities. All in all they're a very well rounded military but a common problem with all European nations... it's just not as big as the four already mentioned, in total 14 million for active duty is impressive but in terms of active troop strength, they're 22. I can't think of any scenario where the UK could take on any of the previously mentioned countries and win unless they are perpetually on the defensive. The UK spends a lot on their armed forces and it shows I considered putting it in fourth honestly and I just might later on depending how many more delays India's two carriers are going to go through compared to the UK's upcoming carriers which are right on schedule.
Next would be France. I would even go as far to say that France's military technology is even better than the UK, the nEUROn, the Rafale, the Charles de Gaulle, the LeClerke, the FAMAS, the list goes on. France has produced a lot of excellent hardware. But France's still isn't as professional as the UK. Their navy though is slightly bigger than the UK's. They're no slouches though and they have a plethora of combat experience (although not as much as the UK). France is only a smidge behind the UK in my opinion
After the sixth place France I would put Germany, Italy, Ukraine and Saudi Arabia in that order. Germany and Italy are self-explanatory. Ukraine is in a unique position is that it inherited a ton of Soviet technology and expertise, and is making active use of it. You would be hard pressed nowadays to find an upgrade project or a development project that doesn't have the Ukraine involved somehow. Saudi Arabia is on the list because frankly, I cannot see how you can spend such an obscene amount of money and NOT get results eventually, the Saudi Army is the most powerful local military force in the Middle East but is far, far too dependant on foreign aide, the only thing from not giving Iran 10th place is that it is a political pariah that has some good missile technology. Iran is currently going through an odd phase where it is gaining design expertise by taking decades old designs and slightly retooling them. It may not seem useful but it's giving them the experience they need. Japan has a good military, dare I say, an excellent military with a powerful navy, but with its population and constitution, Japan will languish perpetually out of the top ten unless it becomes establishes a more dedicated defence industry. Japan is capable of producing good equipment, all of Japan's AFV's as of late are very good, it's a shame thought they most likely will never see any action. Pakistan is pretty much a joke in my opinion. Taking a Chinese design and calling it your own doesn't mean you're design genius'. South Korea has a lot of flashy things going on for it, lots of money is directed at defence right now and they're certainly a rising star, if they keep their current pace up, they might make the top ten. Notice how I didn't put Israel? Israel in my eyes, lost a lot of respect with their 'loss' in Southern Lebanon, I find it hard to believe sometimes this is the same army that won the Six Day War.