There is nothing new about "Metroid Prime Trilogy." Every bit of every one of the worlds in it can be found in other games, games that range from two to seven years old. If you knew your way through the games when they came out, you'll know your way through them now. This is old material, recycled for the sake of making money off a known property.
And all of that is just fine, because the "Metroid Prime" games are some of the best games released this decade.
"Metroid Prime Trilogy" turns the sublime trick of dragging the first two games into the current generation by replacing the analog controls of the first two "Metroid Prime" games with the motion controls of the third. "Metroid Prime 3" continues to be the standard-bearer when it comes to first-person motion controls on the Wii, and they are applied to the first two games flawlessly. Even if you've played the first two games to the point of memorization, playing them with the new control scheme somehow feels fresh and is entirely worth the experience.
Also added to the first two games is the medal system of the third, an achievement/trophylike system that rewards you with different-colored medals depending on whether you defeated a boss, found a particular bit of equipment or even scanned enough different things to warrant it. The medals can then be used to unlock various extras, from soundtrack cuts to art galleries.
Of course, if you haven't played any of the "Metroid Prime" games yet, this is the best chance you're going to get. At $49.99, you get three full games, all of which were and are game-of-the-year quality on their own. Even as a product that only repeats previous games (albeit in a new way), "Metroid Prime Trilogy" is bar none the single finest single-player experience the Wii has to offer. You know what to do.