If you like games like Thief you should like Splinter Cell more. It's more about stalking your pray and sticking to shadows. A lot more tactical.
I would say MGS3 fits that bill much more closely than any of the Splinter Cell games, except replace shadows with camouflage. You have to stalk, incapacitate/kill enemies, or just slip by in a jungle environment. You can go into other areas to destroy their ammunition/food supplies or cut off reinforcements. The whole thing just conveys the hole sense of being a predator stalking its' prey much better than the Splinter Cell games. Although I haven't yet played the next gen version of Double Agent, the others generally revolve around shooting out lights, incapacitating guards, and moving forward through the level.