I'm an old-timer - 1E was my first game, and HackMaster is still my core game system (without all the silly stuff), and I don't allow evil PCs, just so you know where I'm coming from.
My favorites are all Dungeon Crawl Classics by Goodman Games. Honestly. They don't assume anything about the world (making them portable), pretty much everything in the dungeon can be classified as "bad", and thus the enemy, and the GM is left to develop the interweaving plot line.
A close second is Race for Retribution by Bard's Tales, for many of the same reasons.
The only problem I have with both is that they seriously challenge players, meaning if you don't want them leveling every 1-2 sessions you have to halve XP awards.