The only way that this is going to work is if everyone starts using some type of map standard (i.e. large map, common everything, average research speed, all victory conditions on just to see if any race excels at some types of conditions, etc.) in order to make this survey work. Otherwise, the results are going to be skewred as hell.
Anyhoot, here's my analysis, from strongest to weakest:
Korath: Damn these guys are tough, if not
THE toughest. If their military doesn't screw you over early on, then the spore ships will, especially once they start putting some engines on those babies. Their economy is surprisingly strong too, more often than not they'll end up with a pretty nice war chest for some odd reason for another until the whole spore-ship strategy screws them over. But what caught my attention the most was the fact that they kept influence-flipping any mining bases nearby their borders. Oh, and their research ability is pretty strong too.
Drengin: I pretty much agree with everyone on the board here on the Drengin. They start out strong, build a crapload of ships, start up wars, but all of a sudden slow down and crash for some reason or another. But whenever they get their game going properly past the first three years, it's tough to beat them, period.
Thalan: Though not terribly militaristic in my experience, they do tend to build up their colonies really fast, along with their hordes of starbases. Often, I'd see half of their planets loaded with improvements and whatnot. However, they don't seem to apply this mentality to their fleets, unfortuneatly, but they still play an impressive game against the others. I usually find myself allied to them due to their economic strength and rather friendly nature towards my race. And they love to spam influence starbases in everyone's turf (which often causes their downfall

)
Altarians: If they ever survive the first moments of the game and get some good planets, then they can become a nuinseance, especially if you're an evil race. Their research ability is pretty good as well. Also, they almost never run out of resources, so their economy never really sinks at any given time, even when they're losing badly. Otherwise, they're average.
Terrans: These guys are the epitome of a wild card: in some games they'll pwn like no tomorrow once several years pass, and in others they're a total weaksauce race. The Super Diplomat ability of theirs does make them difficult to trick in terms of trade, but it becomes useless near the endgame once everyone is obsessed with war. The Terrans usually tend to dominate the mid-game, but they start to lose their strength by the end for some reason or another, not sure why.
Yor: Hmmm... hard to say on this race. The miniturization bonus they employ is damn nasty, making their fleets tougher than normal, along with their new Super Isolationist ability which can totally screw over your invasions, but otherwise, they're kinda weak at times. I believe it's because they spend more than they can efficiently sustain in terms of fleets and populations, both of which they have in droves. However, due to their aggresive nature, they very rarely survive any of my games once some of the bigger alliances appear.
Arceans: My experience with them has very often shown that they have a horrid opening game strategy, a poor economy, poor diplomacy, average planets, and will only improve if someone saves their ass from elimination or mediocrity early on. But once they do get their footing, it's just like everybody else says: they're unstoppable... except in the research department, where they suck no matter how hard you try to help them.
Krynn: I really don't know about these guys. Not once have they ever become hositle to me or my allies, and they hardly seem aggressive or expansive. Heck, they don't even use their spies for what I can tell! I'll have to leave their judgement to you guys.
Korx: Since they're evil, they're obviously gonna be aggresive and wield a big military, which is always good for the AI in most cases, but the problem is that they don't know how to use it for crap! Furthermore, they'll trade away alomst anything they got for pittens, so if they have something valuable like one of the extreme colonization techs, you could probably get it on the cheap, especially if you're a Super Diplomat! But the worse part is that they don't even use the Super Trader ability effectively, so that just makes them even weaker overall. Definately not one of the better races.
Drath: If they ever manage to find a cozy spot in some distant corner of the galaxy to cause mayhem via manipulation while not being bothered, then it's all good for the Drath. But if they don't, they're screwed...
always.
Torians: While they may breed like rabbits, they sure as hell don't know how to fight, even if their lives depended on it (which it often does!) Even worse is the fact that they don't know how to build a planet for crap, and their severe overpopulation very often leads them to their ruin very early onward. It's rare to see them survive to the end of a game, and when they do, it's most likely because of a strong ally who protects them (who often happens to be me

). Hands down a crappy race.
Iconians: There's nothing redeeming about these guys. Period. Despite them having a +50 espionage bonus, they never spy, and the their colony rush tactics are often flawed. The only thing that keeps them from going extinct in most cases is the fact that they can do a mediocore enough job in the research field, but that's honestly it.