Soldier was my favourite in ME1. People said soldiers were boring but I dunno, I just felt instead of the 'futuristic super powers' feeling that biotics game you, soldier gave you a 'futuristic combat soldier' feeling which was still awesome.
I'm excited for ME3 but for me the second was a step backwards in many areas, mainly things like skills and weapons/armour. I'm not holding my breath, but if they can fuse the polish of 2 with the expanded mechanics of 1, 3 could turn out really great.