The reasons that people usually cite for hating bush are the same things Obama promised to stop and yet continues.
Bush - Iraq/Afghanistan
Obama - Iraq/Afghanistan/Libya
Bush - high deficit/ high debt/ climbing unemployment
Obama - higher deficit/ higher debt/ promised unemployment wouldn't go above 8% and it went above 10 and is now above 9
Obama promised to end guantanamo within a year and did not, and end military tribunals but yet still continues them.
But these are mostly domestic issues, i guess Obama is nicer to the international community while Bush had an America is Number 1 mentality.