I think it would've been rather hard to revive WCW due to the fact that WCW had nothing special in the manner of which ECW had.
ECW was popular due to hardcore matches, something WWE tried to throw in there with the revival of ECW, if WWE was to revive WCW they would simply revive another promotion that didn't have any particular going for them in terms of match styles, with the exception of one giant faction that went on for a few years, which wouldn't be enough to create a show around.
Especially due to the fact that the majority of those WCW guys weren't with WWE when the revival of ECW was created, something that was completely different with ECW, because the people for it, were around, we had Sandman, Sabu, Tommy Dreamer, RVD, the originals to say.
So due to the fact that reviving WCW wouldn't have given anything out of the ordinary thing that was going on in WWE, I think the better choice was to revive ECW because it brought back some hardcore matches, gave something of old that could attract the old fans.
And sure old WCW fans could've returned, but in truth, the booking of WCW wouldn't be the same as the old, because it wasn't any different.
I think WWE made the right choice - ECW