BC2 and MW2 in my opinon are two different games entirely.
I've got to about 4th prestige on MW2, played it for months, and loved it. Its completely crazy and I loved running round with the intervention getting point blank kills etc.
But BC2 is so awesome, because its a real team game. I play with friends, and it is far more fun, as you need to work together to win. Yes, its more clunky, yes its not as graphically awesome, but it feels more "realistic" (I use that word losely!), maybe the word I'm looking for is rewarding.
I used to play Battlefield 1942, and vietname etc, and BC2 is a real step in the right direction for making these big open multiplayer games more exciting. Its not a case of respawning miles from the battle with the new squad system, and soldier classes are far more assorted, with extra gadgets.
Although I enjoyed MW2 alot, I think it went abit too far in the killstreak area, and relied very heavily on fast paced action. BC2 relies much more on strategy, positioning, and group tactics. No you cant no scope with a sniper rifle while jumping, you can't throwing knife a guy for 1st blood, but you can have alot of fun =)
As for the singleplayer, dont bother. Its definitely a multiplayer only game, the singleplayer is boring at best. MW2 does win here.