Why would you change graphics? I don't see any reasoning behind that; would it make the game better? It's the gameplay that made that game great, and I think updating graphics just for the sake of it doesn't serve any real end. Why do we need to "upgrade" a game just because new technology is available? I wouldn't care for any additional glitz and glamour, it would just seem out of place. They made ports of the game because they didn't feel like the game warranted any changes; when people play a classic game, I'd imagine they wanted to play the game that they'd heard of so fondly by others. If it were changed, it wouldn't really be the same game again, then would it? This is why I'm generally against changing an old game substantially -- I don't understand the reasoning.
As my blatantly overt ramblings convey, I wouldn't change a thing. Sure, the graphics were dated and the game was hard, but I like it, dagnabbit. Now you kids get off my lawn.