Nash's best matches were with Shawn and Bret, who could have good matches with anyone, but outside of that he sucked in ring.
Promo wise, he was able to get away with a lot of shit that other guys couldn't do. It was new for the time, but it got old. The most memorable Nash promo is the one he botched, "look at the adjective... play!" But outside of that, you can't remember anything from it. I always thought he was average at best. I actually think his TNA run is a lot better than his WCW and WWF runs. He was far more comfortable on the mic and since he was never going to get a mega-push, his promos worked better for upper/ mid card.
Looks, he's a handsome guy which let him stand out from other giants at the time which were usually ugly motherfuckers. I could see why Vince pushed him, but he didn't have the ring skills and average at best promos, so it didn't translate well.