Let's see... 2 biggest WoW streamers are not streaming atm(Sodapoppin, Towelliee)... Also none of the other top WoW streamers(that I can recognize) aren't streaming either.
Also a lot of the ESO streamers are WoW streamers.
Blizzard games are the most popular games(longevity-wise) that's for sure.
The eSport games(DOTA 2/LoL) can't be really counted as they have tournaments going on every day and the streams are literal cancer in terms of viewer-streamer interactivity.