This collection
http://www.amazon.co.uk/George-Gershwin-Collection-Various-Artists/dp/B000I2KPHS has a lot of, well, not quite contemporary, but 'almost' versions of the classics. And has the 8 minute version of Rhapsody with George at the piano.
This other collection
http://www.amazon.co.uk/Essential-George-Gershwin/dp/B00008GEOT/ref=sr_1_1?s=music&ie=UTF8&qid=1313065058&sr=1-1 has some shoddy contemporary readings of songs, but also the best versions of a few of them, like Gene Kelly's 'Love Is Here To Stay'.
Also, picking up a copy of Bernstein's Rhapsody In Blue/American In Paris/Concerto in F (The triple bill Gershwin's orchestral work is usually sold in, although there's more and it's good) will be one of the best things you ever did. Accept no Previn, although he's good. But Bernstein is better. It is, after all, BW's preferred Rhapsody.....