Nope. A great system makes a mediocre recording sound mediocre. There are lots of systems that make everything sound mediocre (and give the illusion that mediocre is somehow good), but that doesn't make them great systems.
Can a great system make a mediocre recording sound good?
I spend a lot of time searching for well produced recordings as they (of course) sound so good on my system (Hegel 160 + Linn Majik 140 speakers). I can't tolerate poor sounding recordings - regardless of the quality of the performance itself. I was at a high end audio store yesterday and the sales person took the position that a really high-end system can make even mediocre recordings sound good. Agree?