D1 and D2 at this point are incomparable. D1 is a compete game, and is meant to feel as such, thus, it is much more fufilling to play, as you feel that any and all progress you make is actually worth it. Furthermore, its incredibly unique in its art direction, and feels fresh, even 9 years later. I would say that if they were to increase framerate and other such things, that it would look better than D2. Finally, it does contain some of the best content on the planet, being Master mode raids. I think the only raid I have completed normaly was vault of Glass.