I really enjoyed PoP, with GoD being a very very close second.
When I PoP came out, I remember how scared I was to zone in to PoNightmare. The music was kind of creepy and I always saw people training the GY. There were all these guilds on my server (Innoruuk) that were trying to advance up the tiers, blocking each other, taking named spawns the were intrical parts of advancing. I was an officer in one of those guilds. I remember calling a target after scouting every zone in PoP looking for mobs to raid, only to be blocked by another guild who was FiF (first in force). It took my guild forver to advance through the gauntlet of PoP. We finally merged with another guild when there was a massive exodus of people leaving EQ soon after GoD came out. Guilds were waring thin and the only way for our guild to survive was to merge with another guild. So we merged and got to the elemental planes, OH!! the feeling our guild got becoming elemental was just so awesome. It was like walking on cloud 9. The elemental planes were nice, killing Xegony and FR were a cakewalk, however Coirnav and TRC were freakin impossible for us. Conquering them was another feat I enjoyed that only 1 other feeling that I could match my feelings with, and that's getting through GoD.
God was a very close second to PoP. I remember when GoD came out, a lot of people were leaving EQ. It was deemed impossible to muster. Going from Natimbi to Qinimi and through Barindu was always scary as hell, being that you never knew if that damn Kyv that sees invis was up or not. When something did see invis and started wailing on you, they hit so damn hard you couldn't even run away from them, they would kill you so fast it was sick. When I did my 4 sewers, Tipt and Vxed, I became KT flagged and got to join a lot of the uber guilds that were already there grouping up. Once again the waring of EQ players was causing a lot of guilds to disband, our guild once again merged with another. We joined the highest guild on our server (Silent Resurgence). This guild was regarding as our biggest and baddest guild on the server. Everyone on the server stood clear of these guys in PvP, and they always won all the GM arena events. Anyway, GoD was so hard, that this guild was stuck in Txevu and could not get past the Mastruq Champion event (iirc). We merged guilds, and after months of work beat Uqua (omfg what a relief) and Ikk 4. Whe got through Qvic, Inktu'ta, Txevu and into Tacvi. The feeling of getting into Tacvi was better than getting into PoTime. No one on our server would get into Tacvi until server mergers (Inny merged with The Nameless) and 2 guilds already had access. Being the only guild on Innoruuk to get into Tacvi was and is quite a feat. IMO GoD was the ultimate test of your guild's strength and tenacity. It tested people's TRUE skills and unity of a guild.
I currently have a 70 mage on The Nameless Server, 500 AAs or so, full CoA/DoN gear +. I really enjoyed PoP and GoD even though our guild has beaten everything else on EQ.