Screw the graphics of D1. I still get more replay value out of it than I do D2 only because its more creepy and you have a higher chance of getting killed unlike these friggin' Hammerdins, Concbarbs, and MAzons.
Back to the topic on hand. Sorry, you can't simply d/l Hellfire unless you use certain grey-area file sharing programs. I do recall, and this is a while ago, that http://www.ebgames.com had Hellfire for sale for 10 bucks.