Seconding Splinter Cell and Metal Gear. Highly recommend Splinter Cell: Chaos Theory if you can put up with how clunky it is, it definitely shows its age. Honestly though, I personally preferred Splinter Cell: Blacklist and would start with that. Plays much smoother, and Is my favorite of the series. Same deal with Metal Gear. If you don't care for the story and just want a good ass stealth game, Skip straight to MGSV: Phantom Pain. The games are all great, but in terms of gameplay MGSV is by far the best, and the rest of the series kinds feel simpler in comparison. If you care for the story though, they're a must play and are brilliant