Yeah, I was kind of irked that EA never released any European Theater maps for BF1943 (although I would almost bet money they'll return to that as the BFBC2 Vietnam-styled expansion pack for BF3). That game was some great, quick shootery fun for a long while.
MP-only games are in a weird place on XBL. There's (at least for me) a hesitancy to buy even the games which look fun because there's no real longevity. There's so much coming out that most folks just move on to the next thing within a month, leaving only the griefers and experts still playing, and there's your $15 pissed away. Who could blame them, though? There is such a volume of quality games coming out that you could miss peak playing times by sticking with an older game and passing over a newer, decent shooter for even a month. Renting and trading drop the player count pretty quickly, as well. On PC there remains a certain player base for almost any game, no matter how old. You can still jump into full servers for BF1942. You'll get your ass handed to you, but they're still out there if you feel like playing. I would have thought that games on console would reach a similar player spread over the years considering the amount of used MP-focused games still selling through places like Gamestop, but for the most part that hasn't been the case.