I'm not an expert, but I don't think so.
It's not like movies that can be upscaled on DVD to a higher resolution, because many of those movies were filmed in a higher resolution than what they ended up on DVD. Such as when people talk about how old black and white films were hi-def at filming, we just never had the technology to play them back as such.
With game graphics, they are built and designed from the ground up with a resolution "cap" already in place. So I don't think that can be raised and improved with out some work being done from the core of the game engine, out. I'm not sure a patch could do that much, hence why most updates to old games are retail releases.
Interesting question. I hope someone with more technical knowledge can explain better than me.
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