UT2k4 is great if you're a "twitchy" kind of gamer. You can be hit by a dozen whatevers from any direction at any moment, so you need to constantly be on the move.
1942 is great if you like WWII combat sims. You need to keep moving (of course) but it does a good job with most of the battles. 1942 also gets extra points for the Desert Combat mod, which is free and a excellent modern combat game.
BFV is good as a representation of the Vietnam war. It does give a new feel to the Battlefield series because it is fought where there's actually cover on the ground, rather than freshly cut grass like in 1942. I'd suggest you "try it" before you buy it, Desert Combat is somewhat better.