I think it's unfair to argue that only the left is interested in progress. The right wants a better world too, it just disagrees on A) what constitutes progress, and B) how to achieve progress. To the right, economic freedom is the best arbitor of change, whereas the left tends to believe that positive change can be instituted.
A truly right-wing perspective would be to deny the very possibility of progress and argue that society is better off perpetuating itself in its traditional, "natural" form. Of course, ideological lines are so blurred today that things work out a bit differently, but the importance of tradition is still a key part of right-wing thought in most countries.
I've rarely met a right-winger who agrees with this definition of the right. I'd say that in Sweden the left stands for tradition and a nostalgic harkening back to the 70s, while the right wants to change and modernize things a lot.
I'm surprised no one has yet proposed the obvious left-wing answer - the left is whatever movement is aligned with the poorest in society while the right is whatever movement is aligned with the richest.
