I go to a relatively small campus, and I am a Melee player. I came up with a format for a tournament that had an okay turnout (I didn't organize or advertise, I just came up with the format). There was much positive feedback. Basically, the two people chose a game out of Melee, Brawl and 64. If they both chose the same game it would just be a Bo3 for that game, but if they chose different ones (say I chose Melee and they chose 64) they would choose the stage for Melee and we would play that one and I would choose the stage for 64 and we would play that one (order really doesn't matter much), and if it was 1-1 then the remaining game would be played on the unchosen game (in this case Brawl). If you have the setups this is a fun way to just play Smash cuz you enjoy it and get away from the elitist attitude that Brawl and Melee players seem to have about their respective games while 64 is forgotten (I still love 64 guys).
Regardless of competition level, even if I just wreck on my main game Melee, if I am not that good at Brawl or 64 I would just lose anyway (unless both competitors chose Melee). This would obviously work best if there was a competitor for each game in the tournament, but I don't have that luxery. Just throwing in my 2 cents.