For me, BF2142 was the pinnacle - though that was a PC exclusive.
They got the balance of progression, skill and lack of three million pointless trinkets just right. BF2 was also up there for me, but I don’t think I’ve played a demo version of a game to death, like I did with the original BF1942.
I’ve tried with the later BFs online - I really have. But the games feel broken and in a way I can’t really convey properly. It’s like they are all glossy veneers of a format without any real substance hidden beneath.
The last BF game that I pumped online time into was Bad Company 2. Since then, each iteration to me has been poor. I buy and play them for the SP campaigns and then get rid. BF1 online for example was shockingly terrible. Almost like a studios first attempt at a FPS - not one expected of an industry veteran like DICE.