When I was really young there was this movie "In Search of the Castaways" that I was in love with and still remember fondly. It's in color, but dates from the 1960s and the visual effects are probably laughable today. That is a family friendly adventure story If you wanted more adult oriented maybe the Pink Panther series with Peter Sellers (well you've probably already seen these anyhow) but that's my all time favorite. Slightly more obscure is something like 'Forbidden Planet' from 1956 which is also in color, and i guess it's the first movie ever with an electronic soundtrack. It's totally awesome, I loved it. Even more obscure- there's an East German flick "Haisser Sommer!" which can be bought on amazon, is a musical all in German from 1968. Was way more catchy and cute than I expected.
3:10 to Yuma - The new one is really good as well. Ace in the Hole Advise and Consent Aparajito Bad Day at Black Rock Battleground Brief Encounter Come Back, Little Sheba Elmer Gantry Forbidden Planet From Here to Eternity Gold Diggers of 1933 H.M.S. Defiant - My favourite of the Bounty films I Confess Kin-Dza-Dza Lili M M. Hulot's Holiday Mr. Deeds Goes to Town Nanook of the North Network Persona Pigs and Battleships Rocco and His Brothers Shoeshine Seven Waves Away\Abandon Ship! Sweet Smell of Success The Grand Illusion The Killing The Last Run The Manchurian Candidate The Night of the Shooting Stars The Petrified Forest The World, the Flesh and the Devil True Grit - Again, the remake was really good Zorba the Greek All of the Arabian Nights I've seen ranged from good to awesome.
I could easily recommend anything that includes Vincent Price. That man is amazing. *.* Especially The Tingler, House of Wax, and A Comedy of Terrors.
I'd also highly recommend Blithe Spirit and Auntie Mame (with Rosalind Russell). Those are definitely two of my all-time favorite old movies! Berserk with Joan Crawford was also really good, if I remember correctly, but it's been a while since I watched it.
My mom raised me to love old movies (especially musicals), so I totally get where you're coming from. She's slowly introducing me to more and more.
A classic that doesn't get quite enough love would definitely be the "Little Shop of Horrors" from '86. Amazing animatronics, great design, songs and actors. (Rick Moranis, Ellen Greene, Steve Martin, Bill Murray)