Fun is what you make of it.
Should I win, that's great. But if I get to play the new card that I threw into the deck because it looks cool, well, that's a victory too, even if I end up having my arse handed to me. Bad puns generated by certain cards are a key point, as well (those involving the Fire Elemental come to mind).
For casual play, especially chaos, player interaction is what is fun. Watch the guy who gets mana-screwed next time. He is not having fun, so is either killed off quickly, or left to linger as he is seen as not being a threat. Victims of LD and/or mana screw know this feeling. Heavy counter/control players start off having fun, but realize they become the target of everyone's wrath, by countering everything worthwhile -- resulting in little enjoyment for anyone (until the control player is dead, at least).
If you are kind and benevolent, you might take to playing party cards -- the assorted Oaths, the variants on Hunted Wumpus, and other artifacts and spells that affect everyone equally (except you, as you build your deck to take advantage of the party card, so you are more equally).
But those off to tourneys, or practicing for them, are there to win. For good or bad, victory means ensuring your opponent does as little as possible (no fun for him). Just be kind enough to warn your potential opponents BEFORE playing them (except in tourneys, attendees should know that already).
Solution? I avoid all tourneys but drafts -- plenty of interaction, as combos are nigh-impossible, and it nearly always devolves into a creature battle (though I did win once last night due to my opponent using Elfhame Sanctuary to draw himself out of cards...). Additionally, I try to get chaos games going constantly. Lots of fun for everyone.
That might be a bit disjointed, but its how I define fun in Magic.