It is interesting to look at how Classic could differ from TLEs from Everquest or releases from Archage and Aion, but if history is repeated, the TLEs in the EQ2 game die fast and aion classic kinah the more expansions that get released the less interest there is in the expansion itself. It is reserved for people who have been playing for a long time and do not shine as the beacon of the community.
DayBreak, which is also responsible for EQ2 It doesn't care at all about WoW players (aka micro transactions in p2w mechanics etc) and are using the game more to in attracting new players and old players to the game which has a lot of issues live, and is often stricken by numbers and mechanics that are bloated.
I don't know what the max is but I'm playing on Siel server at Aion Classic and it's super bustling during the day as well as in the evening (I'm NA East). It's very enjoyable and the server is very crowded by EU and NA players. I would recommend joining us. :)
After further investigation, i am not joining, mainly because of the organization behind aion. I don't have time to catch up, I'm not the biggest whale, and it will be an absolute nightmare to win.
Asmodians can also be a problem for Elyos often in Heiron In some cases, they go so that they even rob those who are farming Aether beyond the gate...Some gank you when you have a half health status from mobs with PVE, or even when you're fighting a mob. It isn't a good idea to lose any advantage if it were yours.
Retail turned out to be a different game. Anything you played with as young is still available which is why I wouldn't suggest it. If you're curious about the latest developments I've included them in my history of comments.
Classic is a good option, but since there are only two servers, they are still balancing out. Siel is more pop-oriented and asmodian heavy, and they control the majority of the depths. This makes it difficult for them to harvest AP at times.
Israphel has lower pop and is more heavy on elyos. They hold about 50 percent of the abyss and the remainder is split between balaur, asmo and balaur, making it more easy to earn AP. I'm NA but I play during EU times. While it's not always quiet but I've never had euro aion classic buy kinah too hard time finding groups.