I played both Nostalrius and Wildstar extensively and the two were nowhere close in terms of scale, depth of world, community, lore, or any other metric you can think of really. The boss mechanics, housing, and soundtrack were great but the game was incredibly lackluster otherwise. Lore had some potential with the Drusera arc being interesting.
As for the bad: PvP balance was a trainwreck. Quests were meaningless as you'd get 30 at once and blow through each on in a couple minutes. Rep grind rewards were poorly balanced. Instances offered little reason to run them repeatedly and relied too much on the interrupt mechanic. The world was much less atmospheric barring some neat zones like Farside that you had no reason to return to after leveling through. Itemization was dull with no interesting items or stats. No secondary professions. No cosmetic pets. Instanced zones. I could go on and on but that touches on most of the major issues.
Oh, and while I love addons they needed to be more careful with just how powerful they could be within their poorly planned economy. I coded an autocrafter for the Architect profession in the first couple days and basically botted (legally) $1500 worth of currency @CREDD rates in a single week. Fun for me but rather unhealthy for the economy itself.
The problem with Wildstar is rather like the problem with trying to get your highschool band back together. The drummer moved to another country, the lead singer has two kids, the bass player works shift work. Everyone grew up and no-one has the time (or inclination) to raid any more.
I think a lot of people (myself included) loved the idea of Wildstar but just weren't in a position to make the investment of time and effort required to really enjoy a game like that.
It's worth noting that Wildstar launched targeting the hardcore WoW raider experience.
It failed miserably since targeting only a single-digit percentage of WoW's playerbase is not a profitable business decision.