Yes, I believe you would have better picture than regular DVDs, even on a non-HD TV. If nothing else, you should be able to enjoy the richer colors you get from HD.
Of course that doesn't mean it's worth buying into a dead format. You'll have to figure that one out for yourself. The only reason I pick up the occasional HD DVD is because I already have the player and enough discs to keep it around. If I had nothing today, I'm not sure I'd go for it. But that's me.