I like both, it really depends on the game. Halo CE I liked a lot, I rushed for sniper and dominated while everyone else used the cheap magnum. Wolfenstein ET is also one where it's not insta-kill, but I found really fun. Most of the time I played engi w/ rifle or CVOP w/ sniper. It's also very very easy to shoot in Wolfenstein ET since you don't need to lead your shots so a lot comes down to how well you can strafe and your positioning(although aiming is required if you play with riflenades).
In the "insta-kill" genre I really enjoyed CoD1, mostly because you could play a very aggressively and win. You didn't need to take cover, you could just rush the fuck out of an entire team and get your +25HP/kill and move on, very easy to pick up and play.
CS:S I found hard to get into because if you were a big noob you would get crushed every single round in the first 30 seconds and then wait 2 minutes for the round to finish. It discouraged me to play anymore since I wasn't having fun nor was I learning how to play better. On top of that you couldn't recover HP so whatever damage you took that was it. The accuracy was another thing, if you burst too much you won't hit shit even if you get the drop on them in close quarters, which is what annoyed me the most when I sprayed with an AK and the asshole turns around and 1deags.