Which do you think is currently the best entry in the series, and why?

Super Metroid.

The areas were all so diverse, and extremely interesting to explore, the controls were just extremely fluid, and the soundtrack is outstanding.

Metroid: Other M.

It's just fantastic. It was dark and fun to play, the gameplay was awesome, I mean you can do a lot of stuff with a single wiimote, that shows you don't need fancy controllers with ten buttons and ten sticks. The story was great, the atmosphere. It was neat. One of my favorite games of all time.

I've only ever played Super Metroid. Great game. I'd probably like the 3D Metroids more, but I'll go with that one.

Metroid Prime 2, it has everything that made the first one amazing with more difficulty and a dark version of the planet and Samus.

Went with Metroid Prime. It was my first game in the series and I love it to death. Though I also got plenty of love for the 2D games as well.

I've played them all, going with Super Metroid. It has the biggest and best Metroid world and the best game mechanics.

For me, Prime 2. It is probably the most atmospheric game I have ever played (Which is saying a lot, even just for this series, which is extremely atmospheric/known for this trait). The bosses, level design, music, sense of dread, etc. were absolutely perfect, IMO. The scans were not as good as Prime 1 (another masterpiece), but damn, the overall package was incredible. It's gradually moved up and up in my best games ever list. I would love for another game like this, especially with modern technology; it would have the potential to look and play so nicely. 

I'll probably be the only one to say Prime 2. Prime 1 and Super and Fusion are also incredible, especially Prime and Super. Fantastic games. 

I said prime 2 as well , and I 100% agree with everything you said

Super Metroid for me...though the Prime are also fantastic.