I'd say it kinda depends on their age.
If they're younger, 4e's simplicity with skills will probably appeal to them. They don't want to fight? Well, you don't need to concentrate on the combat aspects so much.
Try shifting around Utility powers for Combat powers, for example. That may let them shine a little better.
If they're older, don't want to do any fighting, and are mature enough to pore through spell lists and manage skill points, 3.5 may offer more for them.
Honestly, though, I'd go oldschool and break out the RC or the Basic set. Most of your roleplaying will be freeform, but hey - that can work pretty darn well, especially with casual or new gamers.
-O