I have to say in the broad scheme of things, there is a lot of balance between the three, but Thunder stacks up on top for me. Although the damage numbers for Ice seem to be higher, I find that in so many of the games, water is a huge part of the enemy base, lending weaknesses to the argument. Although on the same hand you could then say fire because of the high occurence of undead. Regardless, I still like Thunder because if I call them even damage and weakness-wise, I like the thunder animations better