Ok maybe not everyone enjoyed the whole black/white thing but I thought it was a nice change of pace for the series.
But thus far the series is a hands down 10, if they made every game metroid style I'd never be bored as I am with 95% of the games today.
No matter what metroid does or how it does it, it always has good mobs to fight, lot of secrets to find, lot of upgrades, many, many different ways of killing mobs, and just hours upon hours to explore the world they made.
And speaking of exploring the worlds always look great and are fun to explore and the design is always great, some times a pain in the ass to traverse the same area 4 times, and I get metroid isn't for everybody, the games doesn't always point you in the direction you need to go you actually have to do that yourself sometimes.
If I end up buying a WII the only games I would ever get would be metroid and zelda there really is no other reason to own anything ninetendo anymore other than those games.
And I think it's extremely selfish of ninetendo to not publish the metroid/zelda series on PC. Nintendo to me which was once the god's of the gaming industry really aren't jack sh-t anymore and I really don't want to buy their crappy gaming console anymore.