Well, first of all they have come along way in the past ten years with developing both better gaskets that hold up, and synthetic oils that have gasket conditioners in it. Remember, back then alot of people had alot of misconceptions about synthetic oils. Like if you use synthetic, you had to do it early in the cars life, and you can't mix conventional with synthetic. Now we sell conventional/synthetic blends, and they have a synthetic specially developed for high mileage cars, even if you had the car on conventional oil for 80k miles.
Mobil makes a good oil. There are better out there, but for the everyday driver and average duty vehicle, Mobile, Quaker state, Valvoline....they are all very comparable in mix stock synthetics. The benifits of synthetic oils now so far out weigh the cons and conventional oils, I don't even think it's a valid question anymore.