To me their early era albums have so many great songs it would be hard for me to choose. I pretty much love them all. The albums Days of Future Passed, Question of Balance, Lost Chord, Threshold of a Dream, Seventh Sojourn, To Our Children's Children's Children. There are no mediocre songs. Every Good Boy Deserves a Favor is a bit weak though. Story in your Eyes is really the only strong song on that album.
There are far fewer excellent songs on their late era albums. Only The Voice (Long Distance Voyager) Your Wildest Dreams (the Other Side of Life) and I know you're Out there Somewhere (Sur La Mer) come to mind.