I think I'm one of the few people that didn't particularly care for Ego. I thought Russell overacted for most of his screen time, was campy at times and Ego's story just wasn't interesting to me. He never felt menacing or threatening to me, even though his powers were obviously very strong.
I thought Ronan was much better, but as I've said around the boards, my preferences for villains are different than most. I like the mean SOB, intimidating villains better. Ronan was mean and intimidating all the way up to the dance off, where the character fell apart. But he took out Drax with ease (though after seeing GotG2, Drax hasn't been as powerful in these 2 movies as his name says he supposed to be "The Destroyer"), took a blast from Rocket's canon and laughed it off, and was just nasty and unrelenting throughout the movie.
Definitely agree with the majority in the thread though that this is not an MCU problem. All studios have had at least 1 good villain, couple other solid ones and a bunch of duds. The DCEU has been almost entirely duds so far, though I thought Zod was very good, one of the better villains in a CBM.