I am very good at FPS and RTS games, but I try not to play any of it any more. Gaming is like a big addiction/idolatry problem to me, and I mean like Alcoholics Anonymous addiction.
I'm not familliar with any of the more recent FPS, but I know there is a very good one that you can download for free and play online for free, which is called "Gunz:The Duel". Just make sure you download the english version. Hmmm...it isn't nearly as popular as the ones you pay for, but it has some very diverse skill levels of players, so even if you hit your threshold, at least there's always starting over and whipping up on the noobs

. I hit my threshold somewhere on the low end of the "K-stylers", and never could get any better, but could eat most "sprayers" for lunch. Fun game and very, very clean compared to the majority of FPS, at least as far as I can remember. There is also a "co-op mode" where you team up to fight the zombies and whatever to earn better gear.
Once you get where you can win a decent amount of team games and deathmatch games with "sprayers", you will need to ask someone to train you in "K-Style" or "J-Style", because by the time you start winning games consistently, the computer will start matching you with the expert players, and this game is FAR from your typical FPS at expert level.
If you are looking to win a game by running around with the chaingun, don't get this game, you'll get plastered...repeatedly. If you are looking for a FPS where the shotgun and the sword/dagger are the best weapons, this is the game for you.
If you want to try something different, try Starcraft, if you haven't already. The game is 10 years old now, but it is still the best video game ever made. You can buy it and the expansion in any gaming store for about $20. It is RTS (Real Time Strategy) and right now the Koreans are the best in the world, as they nearly always have been.
Just search youtube for "starcraft Korean pro gamers" and you'll get hundreds of videos of watching the very best vs the very best.
The only problem with Starcraft for multiplayer is that it is a LOT like chess, as a noob, the skill gap is almost impossible to overcome. You will lose fast and often for your first several dozen to perhaps several hundred games. I guarantee it. I had played the game for about the entire 10 years, ~10,000 multiplayer games, and am still considered a "c-" player.