Hi guys,
Out of the following,which forum software is most popular and what features makes it popular?
1.vBulletin
2.SMF
3.Invision Power Board
4.phpBB


Apart from above, are there any other good forum softwares?

phpBB is free, the others are (according to me) quite expensive.

Invision is quite good. I like it a lot. Though, as Loki said, it costs money. So phpBB has the best bang for the buck. You can't go wrong either way.