The next best thing to Splinter Cell; not sure why I haven't played it before. Anyway, The stealth suits and the gameplay mechanics are cool, but every area you move to seems to have 1 or more enemy than you can mark, often resulting in being detected because you can't eliminate them quickly enough. And even if you did manage to eliminate all that you saw, if you are detected before you can eliminate all in that area or someone finds a body, all the enemies magically know you're there and you can't use stealth anymore - EVEN if you're still in stealth and they can't see you - it's really annoying.
Also something that is very unrealistic - but doesn't break gameplay - is that you can put a suppressor on a .50 cal rifle and the rifle will then be whisper quiet. IRL a suppressor would just bring the bang caused by expanding gasses to be more tolerable, within hearing-safe levels, the shot is still VERY much audible; the same actually goes for all other guns, but seems so much more ridiculous with the .50 cal rifles.

holds up well 12 years later but the ending is total bs