Last night I was thinking hard about this most significant of questions. I wanted to play a game where I could be, or have on my team, a magician of immense power who could blow things up. But I couldn't really think of many, at least not near at hand. I hope you will suggest to me the games that allow you to perform the most awe-inspiring feats of magical destruction (if you really want to mention other non-magical games that's alright I suppose, but I'm definitely in the wizardy mood and definitely not in a bazooka-y mood presently =) Some of the ones I considered and discarded are below, with thoughts as to why they cannot possibly compete for the grand prize...
Oblivion takes multiple fireballs per enemy (obviously too wimpy) and the fireballs you throw never look GIGANTIC.
I considered Jedi Outcast/Academy with Force Lightning, which would be pretty good, but even then I know I would spend a lot of time not blowing things up. (The fact that I considered it suggests that it doesn't necessarily need to be fireballs, just massively unfair magical destruction).
Neverwinter Nights 2 would of course let me make a wizard, but D&D is balanced for all classes to be good, which means the fireballs can never be that much better than a sword.
Aesthetically, Dark Age of Camelot's fire wizard spells had some nice noise and flash to them, but of course that has to be balanced as well, so you're a fragile man in a linen robe.
It's not all about flash and noise, though. Some turn-based RPG of yore or modern-day yore would also be fine, but only if it was balanced so that I could destroy veritable armies with a flick of my wrist. (If I sacrifice all other skills in favor of blowin' stuffs up, I hope I will become terrifying).
Magicka gets a bit repetitive since I haven't got anyone to play with, and anyhow that's more in the comedy-bungling-explosions genre than the it's-stupid-that-you-can-summon-THAT-much-fire genre.
that's all. =T
Partly I ask this game because I want to play it, but partly also simply because I was surprised that I couldn't think of a promising candidate. =)