As others have mentioned Aigis was great because it was an all round great game.

One of the things that I REALLY liked about it is the fact that a working joe like me could put in a few minuets each day and be successful. Most of the other games want you to sit there and watch your character do the same thing over and over....

Aigis was really nice to casual gamers that didn't have a lot of time to play.

I learned a lot about what makes a good balanced web game by playing Aigis. Making a web game is one of those things I want to try eventually too.