I've been here over 5.5 years now and have been an elder quite awhile, one in training in Rift and full elder from the start of Guild Wars 2.
Things that keep me here:
1) Our credos and the fact most everyone follows them. I can honestly say as an elder in the past two months I've only had to deal with two things breaking the credos in our ESO community. Not bad for over 300 members there now with at least a 100 of them near daily regulars. I do not feel like a babysitter as an elder and shouldn't have to be one. In other guilds where I've been an officer, I got fed up because it was like trying to entertain children that needed to be in detention for their attitudes.
2) Everyone is very helpful in and out of game. People have sent people things, helped people with money, helped with information, helped move things, etc. A lot of people in the family do things to help others without worrying about what they will get out of it or what it might cost (time, money).
3) Most disagreements are usually worked out after people cool down. Some times they don't since we are all human and people leave, but overall, the people that stay know how to deal with life as emotional and passionate people.
4) FUN! We like to have fun and try to include others in it. It's what got me here in the first place way back in Warhammer and what made me wind up one of the associate warband leaders during Fog's events there. This was even before we got merged into the Badlands server where we expanded on this fun calling it the Battle for Badlands. Now we do epic stuff like this in both GW2 WvW and ESO AvA. There are still the random pranks, the definite must dive off cliffs as short cuts, and other fun mayhem included.
So I've been in other guilds as well, mostly for roleplay purposes through the games and I have to admit very few guilds I have ever been in made me want to stay like Gaiscioch. I actually pretty much quit everything, but Gaiscioch and one other guild in ESO due to people not knowing how to repsect each other or thinking you have to RP what they want or your being mean, or a miriad of other simply selfish reasons.
There is only one other guild, and my brain can't remember the name any longer, in EQ and then moved to EQ2 that even came close to what Gaiscioch is with how the people treated each other.
This is a very special place and it will SPOIL you into knowing the right way to dealing with people. =)