Metroid Prime 3: Corruption
Prime 3 is shorter than its predecessors, clocking in at about 14-16 hours for a first play through. It's also fairly easy, at least in Normal mode; I only felt like I might be close to dying for two boss battles, neither of which was the final one. But regardless of that, it is a damn fun game, and is really a blast.
One of the biggest differences in this installment is the storytelling, which I've hit upon before, and which Brad has described the effect of very well. In both the first game and Echoes, Samus was almost always "too late;" you could scan nearby objects for informative Lore, but these events had already happened, and so the story was more archaeological than interactive. In Corruption, it's both - there is still Lore, in fact I think more of it than in the previous two games put together, but a considerable amount of significant events actually happen as you encounter and drive them. This more traditional form of storytelling is even more powerful when combined with retrospective Lore entries you'll encounter after the fact.
The controls, of course there will be a learning curve if you're new to Wii shooters (I was), but they are really a dream when you get the hang of them. The graphics may not be what you'll get from a PS3, but they look good, and the environments are detailed with the utmost care. The soundtrack is one of my favorite things about the game: more so than the other Primes, I feel that Prime 3 has very emphatic and powerful battle themes.
I still consider the first Metroid Prime a remarkable work that I don't think Corruption can pass in artistic merit - but number three is definitely more fun to play. One of the most fun and interesting games I've played, in fact.
Progress: 100%, finished Normal mode