P99 is definitely the go to suggestion for EQ as the player base is high and it’s a pretty accurate classic era server. Some of the pros can also become cons tho. Everquest is very much a group oriented game but that means if you have limited time you might be spending your entire playtime waiting to get into a group. There’s no boxing allowed and not every class can solo or can only solo once they reach a certain level. Just stuff to keep in kind.
There was a Warhammer one I found a while ago. seemed to have plenty of people. Return of Reckoning I think it was called. That was a fun game, and I’d probably even enjoy PvP there and I normally hate PvP.
Have you ever tried City of Heroes? The Homecoming server opened up a couple months back, and it has thousands of players on it.
It’s been my favorite private server experience of all time. The population is huge, the players are generous with supporting the server financially, there’s no pay-to-win cash shop, and the game runs flawlessly – I haven’t run into a single bug in a hundred hours of playing there.
If you think you’d be into superhero MMOs, I’d give it a shot!