To show off what a good blu-ray home theater (surround sound, tv, whole nine yards) system can do:
The Hurt Locker (brilliant use of sound, damn good movie)
Black Hawk Down (Best audio and video hands down)
Gladiator (classic, good sound, video's definitely not to bad given it's age)
The Dark Knight (classic, lots of dark levels too)
Iron Man (great sound, lots of fast motion, great way to show off a 240hz LCD or a plasma)
Terminator Salvation (good black levels, very loud, sure to piss off neighbors)
Star Trek (2009) (lots of bright colors, great for showing of an HD set, good sound too)
Final Fantasy VII: Advent Children (the pinnacle for CG on blu-ray till Avatar hits)
Flags of Our Fathers and/or Letters from Iwo Jima (amazing sound, phenominal movies)
Zombieland (may catch flak for it, but hey it's the only comedy that actually makes use of blu-ray. and it's a good movie)
Anything made by Pixar
Cloudy With a Chance of Meatballs (excellent color palette, not bad for the kids either)
I've personally owned a blu-ray player for a couple weeks now, but I've experienced (yes, proper wordage there) those movies in their blu-ray goodness for quite some times (gotta love friends with ridiculous credit scores). To this day, I've not come across a BD as impressive as "Black Hawk Down" which, despite it's age, made the jump from DVD to BD flawlessly IMO. Impressive palette of colors and amazing audio work make it one of the best BDs out there.
Movies to avoid:
Fantastic Four: Rise of the Silver Surfer (though, may not be too bad when 3D goes full swing)
Almost any comedy (sure, they'll look pretty, but most of them have nothing on the above titles in terms of overall visual/audio quality, and despite what Amazon.com thinks, Jennifer's Body was bad but not a comedy) srsly
http://www.amazon.com/s/qid=1265308268/ref=sr_pg_3?ie=UTF8&rs=163357&bbn=163357&rh=n%3A130%2Cn%3A!404276%2Cn%3A163357%2Cp_n_binding_browse-bin%3A387547011&page=3Transformers, either of them (unless you just want to show off visuals and audio and absolutely don't care about things like substance)
any Disney re-release (sadly, none of them so far look or sound much better than standard DVD. really had high hopes for Sleeping Beauty, too)
Wizard of Oz (same boat as Sleeping Beauty. sorry, Toto, no Hi-def Kansas for you)