I'll elaborate on that, and I'll say that all Dream Theater's "easy" songs are great, and never cheesy or commercial for the sake of wanting some airplay.
I Walk Beside You? wonderful uplifting tune, catchy as well, puts you in a good mood. Forsaken? awesome chorus, the best one in Systematic Chaos, it somehow reminds me of the Awake days, a gorgeous power ballad concise and to the point. Wither? Delicate and awesome ballad with wonderful melodies and gentle, delicate playing that shows that DT don't always have to show off. Even You Not Me is good, Desmond Child was hired to make it more catchy and that's what he did, if pop songs were this good, I'd listen to pop.
And so on and so forth.