1. * correct 2. You're prettier than you ever were. 3. You're prettier than you have ever been. 4. You're prettier (right now) than you usually are. 5. You're prettier than I expected. 6. You're prettier than I ever expected you would be. Ect, etc.

I think you can sort this out for yourself, can't you? The first one's fine, the second obviously has the wrong form of the verb, and the word order is strange in the third one.