I have been online at midnight... In WoW alone, I've participated in 7 (soon 8) expansion launches, but that doesn't mean it's an ideal time.
5:00 would mean, people could set the alarm, an hour or 2 early and get some play time before work/school... Midnight (for most people) means it starts 1-3 hours after they should be asleep......only to loose even more sleep, because that's the start time.