Damn, good question, in no particular order....
San Quinn - to me the tightest most lyrically skilled emcee on this planet right now. Just blow the fuck up already!
Biggie - it aint no thing, 70% of my collection is West coast but to me dude is still GOAT. No one can touch his delivery and power to tell a story.
E-40 - my favourite, the uniquest style in the game, the most consistent, and more than anything else, 40 just makes music that I love.
Celly Cel - okay who feels me on this one? B-Legit it hella tight to me and on a single track way tighter than Cel, but not consistent and not top ten material. I used to think of Celly like I do Quinn now, that he got the skills to blow up for the West. He never did but his flow still gets respect from me.
Tech N9ne - you only got to hear his albums to know why. Unique mo'fucka and he is re-defining skills on the Mic. This dude taking it to a whole new level. There was no way I couldn't put him in a top ten.
Tash of the Liks - okay, I'm prolly the only one who'll have this dude in my top ten but damn, he has probably my favourite flow in the whole game. Every thing he's on I just feel his delivery to the fullest. To me he is easily the most underrated mainstream rapper.
Rakim - you see this rap game, it really sounds like hard work for some cats, but Rakim always flowed like it was easy for him. The first emcee I really appreciated for having skills rather than just spitting some words. I would say Erick Sermon for similar reasons.
Redman - for real, I know dude is kind of funny but does he ever not just flow on anything and anywhere. Every album he just rips it up effortlessly. Dude can rap till he's dead and always come funky.
Nas - come on now, Jay-Z is nice at times but this dude is the emcee of the two. One of the only East Coast cats who have put it down and stayed reasonably true to lyrics and skills throughout their game. I'm trying to forget Ooochie Wally at this point.
Ras Kass - for putting nothing out for so long he doesn't really earn a top ten place but I still think back to when he was comfortably the most incredible emcee on the come up, and then think fuck.. how can dude not be in the top ten.
Here's some cats who just miss out:
Brotha Lynch - I only got into this shit from Loaded and EBK4 then started getting his old stuff so I don't have this one on lock like I should, I just know that dude has incredible power to tell a story in a tight ass way. If I'd been listening from the get go Lynch would be top ten fo' sho.
Keak Da Sneak - For a lot of people this shit is like the Emperors New Clothes. Not everyone will admit it, but for real, half the time I don't know what he is saying. But... dude is hella unique and you can feel his flow even if you dont get his rhymes. With 3XKrazy it was off the hinges, but he hasn't put a solid back to back album out yet.
Mac Mall - One of the cleanest flows out there, but you kind of feel he never really stepped it up to be one of the best of all time.
Scarface - consistency and delivery.
Big Pun - Just because.
Snoop - Just because.
Pac - Just because. Incredible appetite for putting out West coast joints, but it is a personal top ten and no apologies that I put him outside it - I admired Pac's energy and the quality music he was putting out, but as a rapper I never really tripped off him.
Couple of East Coast cats: Pharaohe Monch, OC, Jeru tha Damaja, Freddie Foxx/Bumpy Knuckles, all are incredible emcees, but all don't have the recent material to back that up so no top ten spot. Jeru's recent album was weak, though Bumpy's was still the shit.
Anyone from Boot Camp Click, all got some of the best flows in the game but I'm damned if I can pick one, and finally Nore - ha ha, say what ya damn like about this dude, but face it - in a rap game that is saturated to the point of breaking, Nore, just like 40, carved out a nice little spot for himself by having a unique spit and language.