Only a few of you seem to want to address how well Vince did with Big Show, Jericho, and Guerrero...all WCW guys. He did a lot for Benoit considering he had little charisma and couldn't cut promos (usually the death knell for a wrestler). Big Show was as big as he was in WCW, the other three all were bigger in WWE.
Post Invasion yes the NWO Storyline wasn't handled well. Lets not forget that Hogan's crowd reaction at WM 18 made the idea of a return to the red & yellow seem like a good idea (thus killing the NWO). Also, no one on here points out that Hall, with a long history of drug & alcohol abuse, was fired from WWE right after WM 18 due to drinking. Those two events (not planned by WWE) killed the angle regardless of how invested WWE was in it to begin with.
Booker T was in WCW a mid card guy and tag team wrestler. Don't tell me about his WCW titles, he got the belt when Hogan, Flair, Savage, Sting, Nash, Goldberg, Hart all weren't around and the company was changing champions weekly. When the company was strong Booker was there for years and was a talented and serviceable performer, but he was never as popular as Hogan, Flair, Sting, Luger, Nash, Hall, Goldberg, DDP, Scott Steiner in his NWO days, Brett Hart, etc...all WCW main eventers before him. He worked steady for several years in WWE, got a World Title run, and faced HHH at WrestleMania. Considering how much more talent was available to WWE than WCW during those times Id say Booker's WWE run trumps anything he did in his last year in WCW.
DDP: Injuries ended his career prematurely, maybe the initial feud vs Taker wasn't a career highlight but he didn't do anything because he couldn't wrestle. That wasn't WWE's fault.
Steiner: Trying to push him as a face when his character was clearly designed as a heel failed but in hindsight some of the most popular "good guys" of all time were largely heel characters who just matched up well vs other heels (Stone Cold Steve Austin was an ego-centric, foul mouthed , alcohol abusing, cheater , lets remember that as popular as Flair was he was almost always portrayed as "The Dirtiest Player In The Game" who also drank & partied to excess and was a womanizer). Still, Steiner's biggest problem was himself. He is incredibly difficult to be around, and has a nasty reputation for his obnoxious back stage behavior. Steiner being himself, and being unhappy he wasn't the company's top star despite a heavy push coming in, hurt him. If he was easier to get along with and more of a team player he could have stayed around for years.
Ric Flair: One poster said Flair was totally wasted in WWE and that his TNA run was much better. I disagree. First, his initial WWE take over story line vs Vince and feud with Undertaker were among the best WWE storylines in 01-02 and he was way over with fans. The Evolution stable was the best group in the business, major draws as heels, with Flair playing a major role as manager and mouthpiece in helping to get Randy Orton & Batista over as main eventers, more than HHH who was too involved in his own storylines as World Champ to play a complimentary role to those two. His IC Title run was one of the best anyone has had with title in over a decade as he regularly defended on RAW & PPV against top competition such as HHH, Edge, Mr Kennedy, while helping to elevate Carlito & Shelton Benjamin (the fact their careers faded afterwards is their own fault, they got huge bumps from Flair). In terms of memorable matches, keeping in mind that Flair was in his 50s at this point and wasn't capable of putting on the kind of matches quality wise he did in the 80s & 90s, he was still good to very good in PPV matches vs Taker (loss), HBK (win), twice against Chris Jericho (win-loss), Edge (win), twice against Mick Foley (both wins), twice vs HHH (win-loss), Carlito twice (both wins), plus he single handedly won an elimination tag team match with no partners (all disqualified at beginning of match) vs The Spirit Squad on PPV. He also had very good TV matches vs Austin, Rock, Kurt Angle (excellent match), HBK in Japan, Benoit (on the road to WrestleMania), and dominated the tag title with Batista from late 03-spring of 04. In terms of individual "memorable" matches I'd say WWE Title TLC vs Edge (Jan 06 Raw) was outstanding, as was his first encounter with Angle in 06, The Summer Slam "I Quit" match win over Foley was extremely entertaining and brutal, as was his IC Title defense and win over HHH in Hell In A Cell (their re match as S-Series, won by HHH in a Last Man Standing Match, was epic). I disagree totally with the poster that said his run was wasted and agree with others that say over all he was treated well.
Kevin Nash: Again, injuries....he was doing just fine as a major face to oppose Evolution post NWO but his continued declining health kept forcing him out of the ring and eventually lead to his release. He did have a good run vs HHH in a World Title feud, personally I think he would have grabbed the title at some point had he managed to stay healthy.
Goldberg: It's amazing when you look at how many matches he won, beating Rock in his debut, beating Lesnar at WrestleMania, beating HHH for the World Title, that his run is considered a disappointment. The disappointment is it didn't last longer, but that wasn't WWE's fault, he wanted to leave, they wanted him to stay. He'd probably still be there right now if he hadn't opted out (Goldberg-Lesnar II, Goldberg vs Ryback, Goldberg vs Cena, etc).
In the end, Vince McMahon's main concern is money...if you can help him make it he can put aside a lot. Remember he hired Steiner despite his terrible rep and a previous bad run with the company that didn't end on good terms ten years earlier. Certainly Nash & Hogan didn't leave on good terms (Hogan gave him Vince the double whammy of testifying against him in federal court and then joining WCW!!!). You cant blame Vince for injuries to Nash & DDP, or for Steiner's attitude, or for Goldberg cho0sing to leave when he was still prominently featured (remember he was still a major part of the show and winning most of his matches right up the very end). Booker T did better in a much more talented WWE than he ever did in WCW when they were strong, Guerrero & Jericho & Benoit got better matches and pushes and became better stars in WWE than they ever were in WCW, Big Show continued to be a major star, and lets not forget how well Steve Austin did post WCW.