Just about every Hideo Tokoro fight in DREAM was great. The fight with Abel Cullum's considered the best of 'em, and arguably the greatest fight in DREAM's short history. His fight with Dice-K was also great; one of the most back-and-forth, fast-paced grappling wars ever.
Eddie Alvarez' fights with Joachim Hansen and Tatsuya Kawajiri were both considered FOTY contenders in 2008.
Aoki's second fight with JZ Cavalcante (in his prime, no less) was also interesting to watch. It's more for people who're fans of grappling than of just fights, but it's great to watch in that sense. They were both two of the most dangerous grapplers in the world on opposite ends of the spectrum; Aoki with methodical submissions and guard-passing, JZ with probably some of the most devastating ground-'n-pound ever seen in this sport's history and a very good submission game of his own (he's the only guy to submit Rani Yahya-- a weight-class up, but still, submitting a Mundials champion's a great accomplishment no matter what.) JZ also gave Masato a competitive fight in kickboxing, so he was viewed as even more of a terrible matchup for Aoki. But the way Shinya dealt with all that was really interesting, and he even showed a lot of heart at one point in the fight (a lot more than his detractors would ever say he has.)
Joachim Hansen's fight with Kotetsu Boku was a very underrated fight. Boku's boxing skills were on full display as were Joachim's grappling skills and punching power.
Kazuyuki Miyata's fights were fun if you like suplexes. They were kind of eh outside of that, though, unless you're a fan of the deeper intricacies of the wrestlefucking style.
Sakuraba-Galesic was great. And Sakurai-Baroni was fun.
Lion Takeshi and Hiroyuki Takaya's knockouts were also great.