[citation][nom]back_by_demand[/nom]Movies can get streamed in 1080p, you just need to let it buffer a bit before playing if your don't have really fast internet, or if you mean you can't download at all then get the internet, it's really cool and they have loads of videos of cute cats[/citation]
The video may technically be the same resolution, but the high compression used on streaming video makes for a noticeably worse picture quality than Blu-Ray. Not to mention that even though some of the streaming services offer Dolby 5.1 surround (often at a lower bit-rate than on DVD), none currently offer Dolby TrueHD or DTS-HD. And yes, if you have a decent surround sound system, it is quite easy to tell the difference there as well.
Don't get me wrong, streaming is great. It's awesome to have a wealth of content at the click of a button. But, for any of my favorite movies, I much prefer to own and watch them on a Blu-Ray disc to enjoy the higher quality video and audio.