Bomberman Quest is probably among my favourite Bomberman games if just for its funky twists on the formula. Stacks of different bombs and equipment, large areas to explore with secrets to find, and a lot of personality. Pocket Bomberman's a runner-up for being easy to pick up and play in short sessions (Jump Game is too good!), though they're not exactly traditional Bomberman games.
I'd argue Bomber Boy and Bomberman GB 2 are the best 'products', since both games have two meaty single-player modes and a traditional battle mode... though they also wear out their welcome pretty fast? GB 2 has some obnoxous level gimmicks, Bomber Boy just drags on for far too long, and there's no passwords to resume in the middle of a world.