Beyond core issues like good schools, low crime and well-maintained property that you see in real estate ads, it's the balance of private and public space that makes a great suburb.
In hot urban areas like Manhattan, all but the extremely wealthy expect to trade private space (who can afford anything beyond a tiny condo?) for incredible public space right outside their doorways. In rural areas, private space is more affordable. In the best suburbs, there's thought given to creating both nice private space - attractive homes and yards with more room than you could afford in a city - AND surrounding public space.
Where suburbs have been deservedly slammed is when little thought, planning and resources goes into the design and creation of public space. And I don't simply mean "leaving enough open space." I mean creating appealing front yards, streetscapes, shopping areas and parks. Walkable communities will naturally emerge if attention is paid to these things. If you design solely for the automobile, to move traffic at optimal speeds and create maximum acres of parking without thought to sharing space with pedestrians or whether there's a sense of place to these areas, you end up with the hideous aesthetics of Rte. 9.
It's no accident that some of our most appealing suburban centers, such as Concord, were designed well before the automobile - and then NOT redesigned solely to improve auto access. It's still quite possible to drive to and park in Concord if you want to (I worked in that town for awhile, so I know). But the Concord Center streetscape is very appealing to walkers.
Great suburban design is not an oxymoron. Suburbs don't HAVE to look like the Framingham/Natick Golden Triangle.