What do you think?

no

I personally like them without. I always mute Let's Plays or w/e they are called and just watch the game footage

I prefer commentary without gameplay. I'm not joking.

Without unless it's seriously funny.

but you need good voice and give soemthign funny to the movie:)

Without of course!

Keep it to a minimum unless you're genuinely being entertaining. I've heard commentaries where the guy babbles on about nothing throughout and I can't hear a damn thing of what's going on in the game (even doesn't shut up while characters ingame are speaking).

I like commentary, but only if:

*It sounds genuine, not faked or forced

*If the gamer is interested in the game and the story (if it has one) and not just keeps talking non-stop and through cutscenes, etc. (often not even about the game)

*If the commentary adds something. If the gamer is unfazed by most things, I don't enjoy watching it. I like to hear (genuine) reactions.

Also, if commenting isn't your thing, don't do it.
I also like to watch gameplay when there is no commentary, just for the gameplay and the game itself. So just do what seems natural to you and do it because you have fun doing it. Don't expect to become the next big thing. You could be, just set the bar really low and just enjoy your thing :)

If commentary is really funny I would watch it, but without it there is no real reason to watch, I would rather play game than watch some walktrough...

It has to be the correct commentary. Not some shit people call commentary.