When I saw a blu ray movie for the first time, I instantaneously saw the difference, the image was so clean so sharp so pretty to look at, it helped that my friend has a 40inch 1080p LCD tv, but yeah their was a big difference for me.
So for comparisons sake I tried a DVD, unscaled of course, and it just wasn't as clear, it was kinda blurry, so for me right now it's blu ray all the way.
The only thing where you would not be able to tell the difference is 2D animation, but then 2D animation has no where near the detail of live action movies.







