Pretty sure that the reason why Super Bomberman 2 is an old favorite is because we only had two choices during the SNES era - Super Bomberman, or Super Bomberman 2. And Super Bomberman 2 is generally superior to the former, in my opinion - more interesting battle stages, character/bomb colors, a more involved Normal Game (fresh enemies, traps, etc.), boss characters (like DF said), and so on and so forth.
After SB2, Europe got Super Bomberman 3, and nobody else got anything more from the series. So a lot of people missed out on SB3-5 - the ones where things got *really* interesting - until the spread of emulation.