One of the few games I would consider to be perfect. It has great gameplay (although the rail shooter segments are kinda inferior to the third-person shooter segments), a pretty good story, great music and some of the funniest dialogues I've seen in a video game. Seriously, Sakurai is an actual comedy genius, and it definitely shows.

The characters deserves a special mention, because the entire cast (except cameo characters like Poseidon) is amazing. Hades is by far the best character, and one of the best villains Nintendo ever cooked.

The game's approach towards difficulty is also one of the best I've seen. You can spend hearts (the game's money) to make missions either easier or harder. The catch is that making levels harder gives you access to new areas, which usually gives you very strong weapons and/or gifts, creating an interesting risk/reward system. In fact, the system was so good Sakurai decided to reuse it in Super Smash Bros.

If you're ever in a position to play 3DS games, this is a must-play. Though keep in mind the controls are notoriously bad, especially for left-handed people. Changing anything from the controls makes it much harder to play, and can actually hurt your hands in some cases (I'm speaking from experience)

If you're still not convinced: the game has a mode where you can spend all your money for a goddess (Palutena or Viridi) to gradually walk up towards the screen until you get a close-on of their face. Peak gaming