Rogue Legacy
The idea is simple. You barge into a randomly generated castle using a randomly generated character, collect gold, upgrade your shit, and find and kill four bosses so you can open the big door and reach the final battle. Progress is saved, so you can scope out one boss at a time, or just hunt for gold and loot.
You won't be able to collect every treasure chest each run because you might not have the necessary ability, so don't fret. Also, you need to use all of the gold on upgrades and equipment before each attempt because the remaining balance will get swiped upon entering the castle. It's all pretty addictiive and consqeuence-free, but some of you might see it as a bit of grind. The different character traits kept thing fresh for me, and so did the moody soundtrack.
I've been playing a lot of good games wtihin a limited scheduled, so I wasn't sure if I would have time for Rogue Legacy, but it respected my time and ability so yeah I would recommend it to anyone who doesn't mind a challenge.