I actually have seen that game, and it looks good. Does it play well? And how are the graphics?
The graphics hold up well, I think, but you have to remember that these games are 10 years old. HD versions have been released, though not here on GOG.
The co-op mode is ridiculously fun. Singleplayer is very straightforward, there's no real story, it's all about fighting hordes of monsters, occasionally interrupted by a gigantic bosses or trap filled rooms. What I like about the game is how challenging it is and how much it rewards skill even on the medium difficulties. When you're up against several dozens of enemies at once, trying to brute-force yourself through the fight via the quick save function won't be enough, real skill is required. Fortunately, there are several difficulty levels, which scale pretty well, so everybody should be able to find a challenge according to their taste.