If you're looking for a retro style, dungeon-crawler game with roguelike elements, then Hammerwatch is the game for you. Either solo or with a 2-4 member party you hack and slash your way through 4 unique acts which have levels (and bonus levels) within them. New enemies are progressively introduced as well as having a boss level at the end of each act. There are five character classes for you to choose from (Knight, Wizard, Ranger, Warlock and Thief) and each character has its own unique trait specific to its class.
With all of the above being said, the game can be quick to get repetitive unless you switch it up often with the characters and the pre-game options. (Such as, shared mana pools, no hp pick ups, no extra lives etc.) I found the game to be most fun when at its most challenging. However, even though the game is repetitive, you can definitely burn quite a good few hours with it: I've played around 60 hours and I still plan on playing more.
Another problem I encountered is more of a community issue. Unless you have friends who want to play with you already or if you happen to be lucky at a certain time of day, jumping into a random game doesn't often get you very far. People are quick to just kick you instantly - which once or twice isn't so bad but I've actually given up on playing the game completely on a number of occasions because everyone that was online just kicked me. However it's not all bad, as I have made quite a few good friends that I wouldn't have had before without this game.
I recommend this game to anyone wanting a fun dungeon-crawler to play that you can enable or disable the roguelike feature at will.