Here is my list.
Heavy Weight
Fedor Emelianenko: Fedor right now is making a case to go down as one of the best fighters ever in MMA. He is 26-1 with his one lost being from a cut in a limited rules MMA match in Japan many years ago. Fedor when he fights always pushes the action and shows no weakness as a fighter. He is extremely tough to takedown even for world class wrestlers and is almost impossible to keep down. When he has been force to use his guard he has shown excellent armbars. Fedor standup is as good as it gets he throws fast combinations on the feet and has solid kicks which he rarely uses. Maybe what Fedor is known most for is his incredible ground & pound that is like no other in the sport. The only thing that can hurt Fedors legacy right now is if he decides to not sign with UFC and continues to fight in Bodog where his chances to fight world class fighters will be limited that will offer little in the terms of prestige and justification for top ranking in the sport.
Randy Couture: Don't let Randy Couture's 15-8 record fool you; he is without a doubt the best fighter in the history of the UFC. He has 3x HW & 2x LHW champion. Nobody in the sport has a better clinch game then Randy. Randy's years of Greco & MMA training gives him a deadly combination of lethal dirty boxing strikes and amazing takedowns that drains the life out of his opponents. Randy also utilizes the fence in the cage as good as anyone in the sport and nobody in the sport prepares as good as Randy. Randy also excels as the underdog and seems that he is like fine whine because he gets better with age.
Gabriel Gonzaga: What a beast this kid is. He is world class BJJ grappler with solid wrestling & kickboxing skills. He shocked the world when he knocked out top 5 ranked Mirko Cro Cop with a high round house kick to the head which has been a trade mark of Cro Cop. With Gonzaga's skills and size he maybe the guy to knock off Fedor.
Antonio Rodrigo Nogueira: If it wasn't for Fedor most people would say that Nog is best Heavy Weight of this generation. Nog BJJ in MMA is unmatched. Nog is always adding new tricks such as anaconda chokes to surprise his next opponent. Nog is not only great submission guy but he has very good boxing skills and is always willing to mix it up and normally comes out on top in the boxing exchanges. Look for Nog to be in the title hunt in the UFC HW division.
Mirko Filipovic: After signing his big deal with the UFC most experts pick Cro Cop to walk right through the competition. After all Cro Cop just won the Pride Grand Prix and most experts agreed that Pride had the better fighters. So that is why it was a shocking to see Gonzaga KO Cro Cop in round 1. That being said all fighters lose even the greats and Cro Cop is one of the best HW of this generation. Cro Cop is a world class kickboxer that has transitioned to MMA. Cro Cop has developed a great sprawl and brawl game in recent years and even when he has been on his back showed good enough guard skills to defend ground & pound & submission attempts. Look for Cro Cop to get back in the title picture with a few wins in a row.
Josh Barnett: Very well rounded HW with great submissions. He holds wins over Nog & Couture. Josh has been a top 10 fighter for almost decade. Right now it looks like Josh is free agent and look for him to sign Elite XC or Bo Dog.
Tim Sylvia: Tim is big as HW's get at 6'8 265 and has one of hardest punches in sport. Known as heavy hitter Tim has shown good takedown defensive & good ground skills up until his last fight with Randy who out classed him on the ground. Tim has a punchers chance with anyone but the UFC & Pride merger it might be difficult for him to work his way up for a title shot but then again nobody should underestimate a 2x UFC HW champion.
Andrei Arlovski: Andre is gifted athletic HW that has all the tools in the world to be the best. He has good submissions and excellent fast and powerful punches. Andre's unfortunately seems to have lost that edge that made him champion. In his last few fights he seems to be gun shy and trying to protect his questionable chin.
Fabricio Werdum: Werdum is a BJJ world champion who is close to becoming a title contender. His striking & wrestling is average but both area needs to improve to be a serious threat.
Aleksander Emelianenko: Alex the brother of Fedor is an exciting fighter to watch. He always goes for the knock out. Alex has a string background in Sambo and has some wins by submission but against the better grapplers in the division he hasn't done well on the mat.
Sergei Kharitonov: Sergie big HW with good boxing and judo throws. Lots of potential here but has not looked that great in last few fights and ground game really needs work to be considered a top 5 HW.
Jeff Monson: Monson maybe the best grappler in the division has improved a lot over the years. The only thing that I think will keep him from becoming a top 10 fighter is his size. He is very short for this division and that seemed to really hurt him against Tim. Monson while a way more skillful ground fighter because of the size difference he was ineffective against Tim even when he had top position.
Brandon Vera: Brandon is undefeated and could be the next big thing in the division lets all hope that his contract problems will be solved with the UFC so we can get to see more of him. Brandon has shown great kickboxing skills so far in the UFC but he isn't just a great kickboxer but also a great grappler but just hasn't had to show it so far in his young career in the UFC
Jake O'Brien: Jake is a very good wrestler maybe the best young wrestler in the division. He still needs to develop his total game but right now he is undefeated and with his recent win over tough vet Heath Herring the sky is the limit for Jake.
Ben Rothwell: Ben very good kickboxer out of the Militech camp. Ben is on a 11 fight winning streak and has been knocking people out left and right. But he has been doing this in the IFL which don't have many quality Heavy Weights but his talent and record can't be ignored