I have a fabulous time playing Dungeon Crawl. While it does lose a little in the graphics department, and there are very few sub-quests, the main quest is very interesting, and very hard. The main quest is "get to the bottom of this dungeon, grab an Orb, and return". One of the hardest sub-quests is "stay alive". Thus far, I've managed to get farthest with a Spriggan Reaper, surviving mainly on spells but doing a fair bit of melee. Spriggan is the weak, fast, magically tuned race who should stay as far away from melee as possible; Reaper is a hybrid caster/fighter, and I'm probably going to kill some orcs next.
The skill system is just suberb. Skills raise when you use them. You need experience to advance levels, but getting experience also gives you points in your skill pool. You can't get better at skills if your skill pool is empty, and you can't choose to save points in your skill pool for later, so most of the boring optimization is out. The only thing left is to choose what skills you want to use, and what you want to raise faster.
Sometimes I miss the fancy graphics, but the gameplay is so much better that I couldn't possibly choose something mediocre like Oblivion over Crawl.
