I'd have to recommend the Magicka game for sure. I only tried it recently but that game is all about magic, magic and nothing bug magic. You create spells by means of 8 keys on the keyboard, using them in combination to create different spells. There are quite a lot of variety of magic spells in the game and it is made with a good sense of humour. The only downside of the game is that it seems to be non-English voice dialogue with English subtitles at least in the first game. Not sure if there are English voice acting options to turn on or not. I didn't mind playing it and reading the subtitles though, they're short and sweet, and the emotion in the non-English voice acting still conveys the humour through and actually sounds kind of funny too. Lots of magic in this game though, and it's apparently a lot of fun multiplayer too although I haven't tried that yet.

There is a sequel to that - Magicka 2, but I don't know anything about it other than that it exists. Neither of these games are on GOG however (unfortunately).

Another game worth investigating to see if it is up your alley or not, is <span class="bold">Lichdom Battlemage</span>. I own it but have not yet played it so I can not give an objective opinion about this one, but the description and some of the reviews sound promising. Worth a look.

Arx Fatalis has an interesting magic system, based on hand/mouse gestures, that also allows you to experiment with spells and discover new ones, IIRC.

Too bad it never goes on sale.

Yes, but I keep on saying the regular price is quite alright for what you get, so if someone really wants to play it that shouldn't stop them.

Nox might be fun as a wizard, too, but I don't remember if I ever tried that.

I have 730 + games here. I think you have me mistaken for someone else.

Would someone mind educating this gentleman?

I literally couldn't use Steam even if I wanted to because of where I live. :P

Okay, ignoring the puss bucket there, back OT Leroux is right.

I only mentioned the sale thing in jest. Arx isn't my favorite game but it revolutionizes wizardry with FPS and really is worth every penny even if you aren't a hardcore fan.

As for NOX, I always considered that more dungeon crawler than RPG.

Well, what are you doing? Would you mind stopping it? Your on-topic suggestions are fine, your curious accusations against tinyE on the other hand are quite out of place ...

Arx Fatalis is a dungeon crawler, too. I don't see the two terms as mutually exclusive. To me RPG is a catch-all term that includes a variety of subgenres, not just the hardcore turn-based CRPG games, but in any case, the OP seems pretty open to different genres and crossovers, so I think it doesn't really matter. :)

In that case let me throw out the original Divine Divinity. Yeah the graphics are a tad aged but you can have a lot of fun with a wizard in that game.

I began recently to play Lichdom and while it has an interesting concept, it's definitely no RPG. It's about experimenting with spells that you don't necessarily need to (so you need to enjoy it for the sake of it or I guess reaching interestingly high damage numbers). It's also annoyingly linear and few enemy variety. Of course if the last 2 things don't matter, it's a good game.

Arx Fatalis is also a cool game, really liked the magic system. I recommend looking into Arx Libertatis as it fixes a bunch of bugs.

Non-GOG games:

Dragon Age series.
Drakensang
Maybes - Skyrim, Kingdoms of Amalur

GOG titles:

Baldur's Gate series
Icewind Dale series
Divinity series
Eschalon series
Gothic series
Inquisitor
Temple of Elemental Evil

Maybes - Blackguards, Pillars of Eternity, Realms of Arcania series, Risen series, Shadowrun series (cyberpunk with magic though),

Interesting magic system? Immediately Treasure of the Rudras comes to mind.

Another shoutout for some of my favourite games like Dragon Age Origins, Baldur's Gate 1 & 2, Icewind Dale 1 & 2, Temple of Elemental Evil, Neverwinter Nights 1 & 2, Drakensang ([url=http://i.ebayimg.com/00/s/MTYwMFgxNTQ0/$(KGrHqR,!igE8g!-0bLKBP(OzYiM,g~~60_35.JPG]look out for this great collection)[/url], Divinity series.

If you'd like some hack & slash, check out Titan Quest, Torchlight 1 & 2 & Diablo II and if roguelike is your thing, then you should definitely check out Tales of Maj' Eyal. Oh, and if in case you're looking to try a FPS with mages & lots of magic (i guess not but i have to try :P), you can't go wrong with Ziggurat.

OOOOOOoooooooooEEEEEEEEEEEEEEEEeeeeeeee!