This same topic was discussed a while back. Bischoff (once he came into control in 93) was responsible for piloting several changes in US Wrestling.
Monthly PPVs (an easy revenue source) were unheard of before WCW started running them after Bischoff came in. Part of the attraction was the free production courtesy of Turner Broadcasting (an advantage Vince didn't have in WWE) but for better or worse the quickened pace of storylines (which affected weekly TV) and monthly PPVs, staples in the US by the late 90s, started in WCW under Bischoff.
Live TV: WWE never did live TV - even specials like Sat Nite Main Event were taped and edited in advance. WCW was doing live TV for their Clash of Champions specials but the idea of weekly live TV was unheard of. Again, Bischoff had an advantage over Vince here thanks to virtually no production costs courtesy of Turner Broadcasting, but other people had that same advantage and did not know how to use it. Don't underestimate the power of Monday Nitro, by early 96, several months before the NWO angle started, Nitro was must see TV for wrestling fans, and several times beat WWE Raw in the ratings between Jan-June of 1996, pre NWO.
The NWO Angle: Its been widely reported that Bischoff saw this angle played out in New Japan (they had a brief co promotional agreement with WCW). Maybe so, but it was Bischoff who brought the idea to WCW and oversaw it's implementation, the portraying of Nash & Hall as invaders from WWE, etc. Hall & Nash's performance and promos, not too mention the Hulk Hogan Heel Turn, certainly had a lot to do with the angle's initial success but Bischoff started the whole thing.
Also keep in mind that in wrestling, many of the best ideas/storylines/gimmicks are one guy's interpretation on someone else's work. The Rock & Roll Express vs The Midnite Express is a red tag team fued in the NWA so Vince McMahon created The British Bulldogs vs Hart Foundation (complete with southern, wimpy mouthpiece manager) to compete. Starrcade was a huge financial success, an event grossing a million dollars in the pre PPV days with ticket prices topping out at $10, thus Vince McMahon created WrestleMania, his version, to compete. Bischoff also had a lot of success recycling WWE feuds of Ric Flair in WCW vs Randy Savage (complete with Elizabeth shocking heel turn and siding with Flair) and of course Flair vs Hogan. Bischoff needed Flair to recruit both Hogan and Savage to WCW, moves the two would not have made without Flair's involvement, but that's not necessarily a knock on Bischoff. Again, other top execs had similar advantages and failed to capitalize.
I think Bischoff was definitely contemporary for the time and updated WCW's look and appearance significantly. He also was the creator of the evil on air authority figure (past on air figures such as Jim Crockett Jr, Nick Bockwinkle, and Jack Tunney were portrayed as neutral personalities who tilted slightly towards fan favorites). There would be no "Mr McMahon" character if there was no "EZ E" as the leader of the NWO.
Now no look at Bischoff is complete without examining how he lost control of the locker room, leaving the roster split into at least three separate camps that didn't work well together, and how he allowed too much say in match and storyline direction to individual stars. There is no doubt, as wild as the industry was at the time, Vince had a much tighter reign on Austin & Rock than Bischoff had on Hogan & Nash, to the detriment of the company. De emphasizing Goldberg at the height of his popularity in 1999, constantly under utilizing Flair, even driving him off television, never having any coherent plan or direction for Brett Hart, these were huge and costly booking mistakes that killed the audience that happened as Bischoff A) Allowed a select group of stars to have way more say in product content than they should B) Bischoff ceded much of his creative authority to people not capable of booking properly.
Bischoff also was not a shrewd manager of money, hence his "ATM Eric" nick name. Several stars got guaranteed contracts well over a million per year, many of the undeserving (Scott Norton, Scott Steiner). WCW was turning huge profits from 95-98 but started bleeding money in 99, thanks largely to Bischoff's mismanagement.
Was Bischoff a genius ? No, there were too many major negatives to say he was. He definitely could not sustain his success so he's no Vince McMahon, and in terms of long term viability, both in quality and popular product content and managing talent, he wasn't Jim Crockett Jr either.
Is he over rated ? I don't think so. I don't see too much proclaiming him a genius in the first place, some fans don't like giving him his due but most of what I see in print indicates he gets much credit for stabilizing WCW and turning them into a profitable outfit circa 95-96, pre NWO Explosion, and for bringing the original NWO storyline from New Japan. He changed the pacing of storylines on TV, greatly expanded the PPV market, and made Nitro a much watch program, which in turn changed the way WWE produced it's product and presented it to fans. He was definitely a success story, not a genius though.