The thing about Ramsey is that he showed the qualities he's showing now to some degree back in his first couple of years at Arsenal, back at Cardiff, and in his youth and early full international appearances. Had Arsenal gone and sold Ramsey my suspicion is that he'd have performed well enough (to his current standard or close) to make Arsenal regret it, and would have been bought again by a top four side.
In comparison Cleverley who has shown nothing to indicate that had he been a 16 year old in the Championship he'd have done anything spectacular or eye catching enough to get a big move. Cleverley could play to his best, and he still wont do what Ramsey does on the pitch.
If anything Cleverley more comparable to Henderson. But even Henderson plays with more confidence in himself, isn't afraid to move with the ball, and has a few more goals and assists in him.
Like you say he's a useful squad player, playing against the weaker sides when the rest of the team is strong. No need to sell him provided he isn't a reason for us not spending on someone else. Because even if Van Gaal was to trust Cleverley to do the job he requires, I personally wouldn't, and even if he played to the best of his own ability, I'd always think there was someone else who could do what he does better and more.
So worth keeping, but more as a squad player than as a player to have much hope for as a starter. If he works he way back into the first team after we sign some others, fair enough.