Bomberman was by no means horrible. Well it was for the price and content anyways, it should have been a 400 pt XBLA title. Instead Konami/Hudson went the $50 route and burned everyone in the process. I just picked it up for $3 at Gamestop and that's about what It's worth. If they released it as a xBLA game I'd probably give it a 5/10 rather then a 2/10 just because of the insulting price.
As far as technically horrible games? I'd go with Yaris for XBLA. Even as free you regret downloading that horrid turd. I can't even describe how horrible that game is in words. It makes me want to punch myself in the face a good twenty or so times, then get curb stomped by a giant roach.
Worst retail disc game? Hour of Victory. Glitch fest with horrid FPS controls (I have played probably upwards to 100+ FPS in my gaming career and Hour of Victory has taken the cake).
Vampire Rain comes pretty close, and Sonic the Hedgehog is the worst Sonic game I've played. Yes, even worst then Sonic Shuffle.
It's just that simple.