Perhaps you should buy the Blu-Ray set and see for yourself. I’ve watched these movies over 15 times each on DVD. I see a slight improvement with BD, but no major eye candy as far as what HD is capable of. I like my new set nonetheless.
If you are comparing large TV's, like 50" and up, there is a significant difference between HD and non-HD, but smaller sets not so much. I had this same issue with my girlfriend because she doesn't acknowledge the difference and it frustrates me. Now she wears her glasses when she watches TV (at least when I', with her)! Cablevision has 2 sets of channels, one for HD and one for non-HD. I bought her an HD set for her bedroom last year, and I'll still catch her watching the cropped non-HD version of a show when it's available in HD, and it bugs me!!