Easily the best sports game in existence. The gameplay is exciting with new mechanics and awesome looking megastrikes, the environments are so cool with stunning visuals (especially coming from a game made in 2007.) The characters are so unique and filled with personality, not a single character feels bland or uninspired. The CPUs are actually very challenging when compared to the other CPUs in other Mario sports games, which is exactly why I can't unlock Petey Piranha, but that doesn't make me enjoy the game any less. The soundtrack is an absolute banger, and then there's the opening cutscene, nothing crucial to playing the game, but holy cow, that has to be the best opening cutscene a game has ever shown me.
I highly recommend this game if you don't have it already, it's an easy five stars for me!