It honestly doesn't matter one iota that I've played D2 for over a decade. I still fire it up between games of SC2 or WoW. D3 just collects dust in my hard drive's sectors.
I don't feel bad at all about D3. It came for free with my year-long WoW sub and it costs me nothing to maintain. It's not horrible, but it's not great. It just doesn't pull me in like D2 does.
Specs and features are nice to compare between the two, but the ultimate decider is whether a game keeps my attention or not. That's all that matters in the end. D2/D2LoD wins out in that department big time.