in chronological order:
Counter strike: my first fps, not much to say here. 1.6 was amazing
world at war: my first foray into cod series, so i think im biased b/c i really liked that game, zombies
mw2: fastest paced, but also a lot of random dying, too many exploits (killstreaks, stingers, rc cars, auto prestige level 10, overly accurate guns), i didnt like this game at all and could list a lot wrong with it. spec ops was cool
bad company 2: i bought this because i was so disapointed with mw2. twas a fun game, sniping was really fun, squads were handy, overall it was a really refreshing game coming from the cod series
cod 4: no real complaints, simple and effective, helicopters were annoying. clearly i was branching out bc mw2 sucked balls
black ops: from treyarch, which i supported, but black ops was a bit boring, guns were all very similar feeling imo, sniping wasnt fun, monetary system wasnt very good, but it had zombies, and gun game etc were also fun,
mw3: ??
BF3: i never really found anything i really didnt like in bc2 except that it was glitchy (not apparent in bf3), and a bit slow, so as time passes i dont think ill find any glaring holes in bf3 either. so far 90% of my playtime has been in a jet, so i dont really know how things are working out on the ground. considering thats about 5 hours of gameplay and i havent even played the fps portion thats pretty amazing. the maps are enormous and there arent choke points like there are in all the cod games. bf3 has a server list!! you can choose what map, what gametype, etc, thats fucking amazing right there. i think i could go on... if you felt the way i did about ^^ those games than you will like bf3 a lot.
more BF3: this is the first game ive played since counter strike that i actually want to get good at