I played BF1942 before Vietnam came out and have enjoyed the newer version each time. I didn't play 2142, the demo was fun but I didn't really enjoy it that much. I threw probably 2 years of my life into infantry only Karkand in BF2.
To piss everyone off: I thought Bad Company 2 was crap. I didn't play Bad Company 1 so Bad Company 2 was the first game that turned Battlefield into a CoD look alike. BF2 had like 6-7 classes, only 4 different weapons for each class, and had PLANES AND PRONE CONTROL. The first game had PLANES AND PRONE CONTROL. Then Bad Company 2 comes out, I am leveling up every match, unlocking redicuous weapons (MG42 is one of the best weapons in the game, so is the Garand and TommyGun).
After acquiring a bunch of stupid perks and weapons, I wanted to fly a plane around for a bit, and learned DICE cut that, probably for the console players benefit. Took the prone command away too, single keystroke was too hard for DICE to implement? Also no bot support.
BF3 was an improvement on BC2. They brought back the huge maps, brought back planes, brought back prone, brought back the classic maps. More logical classes (STILL ONLY 4, WHAT HAPPEND TO MAKING THE NEXT GAME BIGGER?)
BF3 also suffered even moreso from CoD's unnecessary crap, the perks weren't as overpowered, you can't get an ammo upgrade that makes snipers 1 hit kills like in BC2, but now there is a long unlock system, even more dumb weapons, and STILL NO BOT SUPPORT.
Now that Battlefield seems to be EA's version of CoD with constant releases I am pretty much done.
The only way I am going to care about BF4 about BF4 would be if they: added bots back, added more than 4 classes, and allowed Steam purchase. If Origin lasts a few years I will probably buy BF4 if its like 10 bucks but I am not excited at all for BF4. BF3 was a great game, but it doesn't seem like it will be improved on with BF4, only extended which is stupid, BF3 is a massive game.