Well, I don't really know, but the first one that comes to mind that kinda fits your criteria is Hero Heel: http://www.mangago.me/read-manga/hero_heel/
The uke dates the b-team guy for pretty much the entire manga before switching to the a-team dude. And I have to say that the a-team guy is kind of a douche, but it was an enjoyable read when it was all said and done. Dunno. Hope it helps.
mmm if I get whats you are saying there is this manga I read some time ago:
http://www.mangago.me/read-manga/moe_kare/
I 2nd "Moe Kare". One of my fav due to the plot twist with the b-team guy & the character growth of the girl MC. I also suggest trying - http://www.mangago.me/read-manga/hirunaka_no_ryuusei/
*I am also a "2nd guy" lover (≧∀≦)
is there a manga exist where main character actually ends up with the b-team guy? like not where the original love interest was a cheater, jerk, already taken... does tht make sense? i read all these triangles but u always know who ends up with main character >. >