Has there ever been a time when an Incumbent presdent had Greater than 50%

I don't believe so. The only one who may have come close was Ford in 1976, although I believe his approval ratings were in the upper-40's at the time of the election, although his approval rating rose to 53% by the time he left office in Jan. 1977.

The other three incumbents who lost re-election bids, Hoover (1928), Carter (1980), and Bush I (1992), all had high negative approval ratings on their respective election days.

If Obama has +50 Approval why would he not get re elected.

...because people look for an excuse to vote conservative.

in the case of Ford, there were underpinnings there since he wasn't elected in the first place, and he had Nixon baggage.

Ford's was around 43% or lower in Oct/Nov of '76. Carter's were below 40% for much of '80.

I think Obama is in a much stronger position with approval from 47% to above 50%. This is around what W. Bush was in 2004.

Carter, Ford, and Papa Bush had much lower job approval ratings in late October than Obama. Obama is doing quite well in job approval with 13 days left.

Maybe, if more than half of the people approve of the President, but many of them think even more highly of the challenger, is about the only way I can picture that happening.

Although it's hard to imagine that scenario, thinking well of both. Certainly not in today's bitterly divided political landscape.

http://webapps.ropercenter.uconn.edu/CFIDE/roper/presidential/webroot/presidential_rating_search.cfm#.UIgpDFGdl60

Short story: Bush Sr. (1992) was at 35% approval in late October. Carter (1980) was also at 35%. Ford (1976) was at 45% in June (no polling on approval available later).

So, it would be very strange for Obama to lose when his approval is north of 50%.