My top modern lines are:
Alternators (Finally realistic vehicles!)
Masterpiece (The 2010 mystery figure should be good)
Classics/Universe (Modern G1 as it should be)
Animated (show accurate robot modes!)

My preferences are for realistic vehicles with a sturdy robot modes. The movieverse has realistic vehicles but many suffer from much weak robot modes. They dont feel as sturdy as similarly sized Classics/Universe and Animated figures.

The most impressive feature for me are details and realism, that why I love Alts and MPs. Gimmicks are only good if they add an extra touch onto a great figure, like the lightup Matrix chest of MP Prime. Great detail and transformation is THE gimmick for me. Anything else is a bonus, but should not be the main feature. Other great examples are Universe Cyclonus and Hound, both of whom I would have got by themselves anyway. Great figures with bonus partners (Nightstick and Ravage).