Now I know most of you PRIDE fanboys are gonna pick Sakuraba. Yes Kazushi beat the gracies with relative ease and beat some really notable guys like Vitor belfort and Randleman. He helped PRIDE become big in Japan.
As for BJ, he revolutionized the LW division, won the title there and won the title and at WW.... maybe I have the timeline messed up but before the Frankie Edgar fight when BJ was LW champion no one... i mean no one was in consideration to be in the same class as BJ.
my pick... BJ
oh and i have to post this, my other thread only has 600 views in over 4 months. Something tells me my titles arent captivating enough. Blue? Thanks
http://www.youtube.com/watch?v=LtdWFNjmFQk
It depends on what part of the world you're in.
I don't really see the comparison. Penn was the better fighter but Sakuraba's legacy has a lot more to it than how good of a fighter he was, not to say he wasn't amazing as well. 
Saku. The guy is a true legend. BJ, not so much a legend. He could have been, but ....yeah.
Bat21 -BJ isn't a legend? Really?
Saku. The guy is a true legend. BJ, not so much a legend. He could have been, but ....yeah.
Sakuraba. It's not even comparable.
both true legends, if I had to pick, I'd say BJ, but a case could be made for Saku as well...
Sakuraba easily
Sakuraba
Chimp Strength -Bat21 -BJ isn't a legend? Really?
Saku. The guy is a true legend. BJ, not so much a legend. He could have been, but ....yeah.
He is, but in my eyes, not as much of a legend as Saku. Sorry for the confusion.
In the U.S.? BJ, hands down.
Sak. But prime bj beats prime sak
I think had Penn have held on to his title against Edgar and been champ up till now his legacy would be considered I much higher regard by recent fans as it currently is. Having said that Saku.... what can I say I'd say his record is more 'impressive' 'significant' etc but then BJ held a UFC belt at two weights something some of the fighters we refer to as GOAT candidates have done. Tough decision...just like a politician I've cleverly managed to avoid giving an answer.
well bj held 2 ufc belts
and he was ripped off in frankie 1
BJ is one of my favorites, but he didn't have a schedule like Sakuraba's. Sure, he moved around in weight some, but Sakuraba never cut to fight in the weightclass he belonged in. He should have been at 170, minimum. Instead it was 185-Openweight. And he fought some of the best at those weights. BJ looks more like a legend on paper, Sakuraba looks more like a legend in the ring.
Ian King - BJ is one of my favorites, but he didn't have a schedule like Sakuraba's. Sure, he moved around in weight some, but Sakuraba never cut to fight in the weightclass he belonged in. He should have been at 170, minimum. Instead it was 185-Openweight. And he fought some of the best at those weights. BJ looks more like a legend on paper, Sakuraba looks more like a legend in the ring.Nice way of putting it!
Team Alpha Snail -Ian King - BJ is one of my favorites, but he didn't have a schedule like Sakuraba's. Sure, he moved around in weight some, but Sakuraba never cut to fight in the weightclass he belonged in. He should have been at 170, minimum. Instead it was 185-Openweight. And he fought some of the best at those weights. BJ looks more like a legend on paper, Sakuraba looks more like a legend in the ring.Nice way of putting it!
I agree. Well said.
good question OP
on one hand you have Sakuraba Kazushi, a Pro/Catch-as-Catch-Can Wrestler who single-handedly ended the domination that the Gracies & Brazilian Jiu-jitsu fighters held on the MMA world stage - and with an exclamation point - as well as taking on, and succeeding against, the larger 'beasts' of the sport as noted by others
on the other hand, you have BJ Penn who, after less than 4 years of training, became the first non-Brazilian to win the BJJ Mundials in the black belt division, as well as world titles in 2 UFC divisions
tough call
I'd say both are legends of the sport, and both belong in the 1st class of any MMA Hall of Fame
2 of my favourite fighters but if I had to choose 1 it's gotta be Saku.
Both legends and in truth there are a lot of similarities in that they had huge wins, close battles against other all time greats and some disappointing losses but all in all I'd have to favour Sakuraba.