I played every patch hard until max/near max gear. The best era by far was 4.0-4.7. Most and best PVE end-game. Think about how many sets you can farm and work amazing for end-game; Ancient Coin, Lunatic Modor (runadium), Sauro Commander, Bastion set, Brazen Aegis (IO/RST), and Hyperion.. That's 6 sets that work for end-game, coming from 5 different instances, and you can still run shit like Danuar Mysticarium (sillus solo instance), Silona instance (void cube), Pradeth (anybody run this?:)), steel rose and a bunch of other stuff. The PVP is also pretty good out in the open world because blood mark camps have people out at all times of the day doing stuff.. There is Kamar and EOB for pvp along with all the arenas and dredge.. A lot of shit to do.
1.5 - 1.9.. no, just no. Not much to do, siege times initially were random iirc. I used to farm a quest that was like kill 49 calydon mobs and receive 10 platinum coins.. rinse and repeat until you have 2,000 coins.. Or you could farm guards/enemy faction and get ap gear. End game was dark poeta and steel rake.. and Grogget was damn near impossible to kill and DP never dropped a gold item. I mean, out of like 30 runs I think I saw 2 gold items drop and the run took forever when everyone had blue gear at 50.
2.0-2.7.. 2.7 was cool when the arena came out. Sieging on land was actually fun but the distance between gelk/inggison was horrible. Even if you kisked properly it just felt shitty, like if you died before you dropped a good kisk spot or forgot. It's not WoW long of a run/flight but it takes forever to get back into the pvp action there, and Silentera was usually empty because there was no point to it.. If they made silentera kinda like tiamaranta eye would have been awesome. End-game was Besh, and while I look back on Besh with fond memories, I can't go back to farming it.. I tried it on another private server and its just so piss easy anymore, and even when its not, it just isn't fun. One good end-game instance vs 4.0's 8 (or at least 6). You could run udas, but that wasn't end-game and really, 2.0 patches were a solo guy's world. Roll a cleric, farm bosses and sell loot rights. Short man or solo Esoterrace for AP.. Naah, i'll pass, I don't wanna play solo all day again just to become a boss thug, 4.0 encourages group play. Skills did start getting a lot better and more interesting this patch.
3.0-3.5
Good patches. Tia eye was awesome.. a lot of people cried about zerging in the eye, but the eye was one of the best things to ever happen to Aion. They put good rewards in a medium sized arena and let players go ham on each other. Can't tell you how many times I had someone gank me while I was on a keymaster and vice versa, good times taking the enemies shit (and sometimes your own faction). End-game was getting better.. we now had 3 end game instances instead of 1 (Rentus, Tiamat Stronghold, DLR). Although Rentus, imo, was total shiiite, the weapons were still awesome and it was worth running (plus mount could drop). So good pvp, decent pve, and sieges all the time!
4.0-4.7. Won't repeat what I wrote above, just a lot of shit to do both pve and pvp. 4.8 wasn't terrible, getting rid of katalam and danaria pissed a lot of people off because they were nice areas, but I did understand it also. They wanted a smaller map (Levinshor/Kaldor) so that players could find pvp more easily. It made sense, but I think they really just messed up the bloodmark camps there, because many classes could no longer solo (or at least efficiently solo) the camps, and so it became very group oriented, which isn't a bad thing but sometimes players just want to log in and get shit done.. Danuar mysticarium (sillus instance) changed and become total shiite this patch, but Linkgate foundry (a new solo instance) was introduced. It wasn't that great, but it wasn't horrible either. I think the introduction of the plume and +20 enchanting were the two things I liked least about these patches. With each iteration of Aion additional power creep is introduced in the form of new items or ways to enchant.. Like in 4.8 you could go to +20.. Why? +15 was enough (hell +10 was enough). Or also enchant gear granted +1 attack and +4 magic boost in 4.8.. which was completely ridiculus and even further separated players who could +15 their gear and those who could not (even in pve). Overall 4.6 is probably the best patch in the history of Aion.
5.0 terrible, but better than 6 and 7
6.0 dumpster fire
7.0 Haven't tried, I assume as bad as 6.0