well , first and foremost it had 3 things that people like :


1. colecting stuff
2. actual gameplay ( tower defense - which were pretty popular in my days - back in the warcraft 3 age )
3. somewhat decent story that didn't revolved around H stuff (h stuff was cool in the begining , but it gets really old really fast. the fact that h content was not forced down your throat is what separated aigis from other h games)




Also the leveling/cc/aw mechanic was interesting even tho it was a grindfest , and units actually felt good to level up becuase they gained significant bonuses