This has already been discussed countless times. vBulletin used to be the standard, but no longer. Quality suffered greatly when IB took over Jellsoft. They also charge you for every upgrade unlike other companies.

Also take this advice to heart: DO NOT use nulled versions of paid forum software. When you buy the software you have to enter the web address that you host the forum on so the vendor can verify that you're allowed to run the software. If you use a nulled version you risk having your forum shut down, among other sanctions.