Games with awesome boss fights?

Prince Of Persia <3

Beat Hazard Ultra's got some great bosses. Also a Boss Rush mode. Need I say more?

Devil May Cry 3 :D (no coop, game from consoles available for PC)

Dark Souls 1 and 2 ,MGS Revengeance and DMC 3 and 4(you said pc only),DMC 2012 ,Lords of the Fallen(like dark souls but i didnt played it),Batman Arkham trilogy and the good old PoP games

Intrusion 2. Its a hidden gem with amazing boss fights. Also magicka for co-op I guess ?

Defiance

Dark Souls 1/2, Devil May Cry 3SE/4SE, Metal Gear Rising. Ys Origin/Felghana, Guacamelee, Diablo 2-3, Torchlight 2, Witcher 2.
All of these should be on PC.

Terraria

If you like really awesome boss fights you should play Metal Gear Rising: Revengeance the last boss and if you ened a challenge play it on hardest mode you will cry hahaha :D

Devil May Cry 3-4, Ninja Blade, Binary Domain, Painkiller games, Pid, Hard Reset, Darksiders

Paranautical Activity, Super House of dead ninjas and of course I wanna be the boshy & wings of vi (if you're into masochistic type of gameplay) :)

How about Portal 2? I found that quite brilliant!

Serious Sam: First Encounter. Probably the biggest boss I've ever seen, it's like you're fighting a high-rise building.

Epic Battle Fantasy IV on epic. Seriously, you get out of those battles almost ecstatic. Also the battle vs Rafflesia took me more than one hour.

The Last Remnant has some pretty intense boss fights in it, if you're interested in a JRPG.

jet force gemini! Bit old but ;-)

Not just Metal Gear Rising, but the entire Metal Gear saga. While in MGR the soundtrack is amazing and bosses are really hard (really really hard in Revengeance level), in Metal Gear Solid games the bosses have certain weaknesses that you need to discover and exploit in order to beat em. In higher difficulty levels, stealth is not an option: it's a must. You should also check out Bastion, and Deus Ex: Human Revolution (In "Give me Deus Ex" mode). Dishonored bosses are usually easy to kill, except for one of them, which will give you a good challenge at the maximum difficulty level. Then, there is Devil May Cry 3 (and DMC too, you know, the latest one). Finally, as I'm running out of ideas, you may like both The Witcher 1 & 2 boss fights, as they require some previous research and preparation.

La-Mulana has some amazing boss fights if you like that kind of game.

FTL: Faster Than Light. One of the hardest boss fights ever.

DMCs, Kingdoms of Amalur: Reckoning

Space Marine final boss!

But seriously, my vote goes to Dark Souls. Even tough some bosses from second one can feel bit copy paste with different looks, others are much fun. And getting to them is even more fun sometimes.

Metal Slug series :)

FF VII Sephiroth :D
Dust: An Elysium Tale - I don't know why but last boss fight remaind me battle from Star Wars 3 between Anakin vs Obi Wan
Duke Nukem 3D - Especially boss from from DLC Santa Clause :D
Bully Sholarship Edition - fighting with Garry Maybe it's not "epic" but still awesome.

hmmm.
the hard reset boss was fun