Don't let the MSPaint-ish graphics or childish-seeming plot and dialogue fool you: This is one of the best metroidvanias, and best platformers, that has ever been made. The gameplay is absolutely wonderful, very well-tuned action; there's loads of things to collect and a wide variety of bosses to fight with them. Music is pretty great, too. If you're not too shallow to get past visual appearances this is absolutely worth a try, and the childishness even gets to be part of the game's charm once you get into it.