lol. Well you are going to get a bunch of different rankings I think.
This is a story only ranking. Game play is quite different between classes as you know and could impact your leveling experience.
1. Imperial Agent. Hands down the best overall IMO. And if you like spy stories, there is no question about it.
2. Jedi Knight. The classic SW story complete with a dual of fates and a love story. lol
3. Sith Inquisitor. Loved this story, especially as a light side character. I particularly enjoyed the end of Chapter 1.
4. Trooper. Interesting story that left me frustrated but in a good way. Life and death decisions, stupid politicians etc.
5. Jedi Sage. Started slow but really picked up after Chapter 1. You are truly a Consular.
6. Sith Warrior. Interesting exploration of Sith politics. The companions are great story wise as well.
7. Smuggler. Funny as hell! Great one liners. But to be honest, the story fell apart toward the end. Good, not great.
8. Bounty Hunter: Good fun and funny in parts. Didn't enjoy the journey however. Mako almost made up for it though.
All my opinions of course and subject to change. lol