BF3 is nothing like BF2. It's like a really bad cross between MOH and CoD: Shitops.
I went for MW3 myself - because I enjoyed mw2 and played it for months - and loved the mw3 campaign which finishes the MW story and spec ops/survival and enjoying the difference in multiplayer (most the weapons are new, the maps are all new, the perks and the killstreaks .. basically everything is new, but it looks the same).
I'd suggest downloading BF3 and trying it. I was like an hour into the campaign before I deleted it, shit was awful. People say you can't rate a game based on the singleplayer, but I've never enjoyed a multiplayer game that had a bad singleplayer. If it looks nad feels bad it generally is.