It's one of the biggest sources of debate among UFC fans: Who’s the best ever? But it’s not really a fair question. After all, over its 22-year history, the UFC has significantly evolved, from rule changes (gone are the head butts and groin punches) to different weight classes. There are 12 fighters in the UFC’s Hall of Fame (one for each year), all representing different eras and styles, and as deserving as they are, fans still question why their favorite fighter hasn’t been included yet.

As if in response to this growing fan frustration, the UFC is evolving again, expanding its Hall of Fame into a four-category system to include not only fighters, but important personalities and individual bouts. The induction ceremony is part of the UFC Fan Expo at the Sands Expo and Convention Center, July 10-11.

UFC president Dana White told UFC.com, “The UFC Hall of Fame has an important job—it not only celebrates greatness but it helps pass stories of the greatest athletes and fights in UFC history on to the next generation of fight fans. We’re looking forward to announcing the class of 2015 and what is going to be a great induction event on July 11.”

The new categories include fighters in both the modern and pioneer eras, the greatest bouts in UFC history and those who have made contributions to the sport outside of active competition. The new inductees join the current list, which includes Royce Gracie, Ken Shamrock, Dan Severn, Randy Couture, Mark Coleman, Chuck Liddell, Matt Hughes, Tito Ortiz, Pat Miletich and Forrest Griffin.

Las Vegas Magazine picks the top 5 most influential UFC fighters of all time

Royce Gracie

In the “anything goes” early days of the UFC, Gracie’s low-key demeanor stood out, as did his ground techniques, which proved devastating. He still holds the UFC record for most consecutive submission victories with 11. The UFC would not look like it does today withou his contributions.

Chuck Liddell

No fighter in UFC history promised more fireworks than Liddell, whose fearsome striking prowess meant quick knockouts; in fact, Liddell still holds the UFC record for the most knockouts, with 13. His bouts with both Tito Ortiz and Randy Couture are about as good as it gets for UFC fans.

B.J. Penn

Before Penn came along, the UFC’s lighter weight divisions were relatively lackluster. Penn changed all that, fighting his way through many weight classes, becoming both the lightweight and welterweight champion. He had his ups and downs, but many of his bouts are all-time UFC classics.

Anderson Silva

Pound for pound, Silva is regarded as one of the best UFC fighters of all time. His records of 16 consecutive wins and 10 title defenses may possibly never be broken, and his fighting style—lightning-fast strikes and comprehensive ground game—make him one of the most enjoyable UFC fighters to watch.

Ronda Rousey

The word “unbeatable” gets thrown around a bit too much in sports, but in Rousey’s case it’s hard to argue with that description. One of the most well-rounded fighters ever, Rousey is relentless from start to finish, and all her opponents can hope for is to make it through at least the first round.