I’m a little late in providing my response, but I’ll go ahead anyway under the assumption that the OP is still interested.
I am a current “Bush detractor” and yes, I’ve been happy with incumbent presidents before so my reaction to Bush is not simply a case of “all Presidents screw up so incumbents are automatically disliked.”
I don’t know if the OP is keeping track, or whether the original question was simply rhetorical, but here is more information that you probably care about (and a little broader than the specific question you asked):
Johnson (elected 1964) I liked him less after his term than when it started. That Vietnam war thing.
Nixon (elected 1968 and 1972) Due to Vietnam, I liked Nixon less after his first term than I did in '68. 1972 was the first year I could vote and I was an ardent McGovern supporter.
Ford (defeated in 1976) I liked him more after his abbreviated term than I did when he took office when Nixon resigned. I voted for Carter, but that doesn’t mean I disliked Ford.
Carter (elected in 1976, defeated in 1980) I liked him less after his first term. I didn’t even vote for him in 1980.
Reagan (elected in 1980 and 1984) I voted for a third party candidate in 1980, but actually voted for Reagan in 1984. Needless to say, I liked him more after his first term than I did at the beginning. I still disagreed with much of his philosophy but like much of the country I was impressed with him as the “great communicator”.
Bush (elected in 1988, defeated in 1992) I liked him more after his first term than I did at the beginning. I didn’t vote for him in 1988, but would’ve in 1992 if not for a much better candidate.
Clinton (elected in 1992 and 1996) I voted for him both times and liked him more after his first term than when first elected. His personal escapades during his second term gave me pause, but I still liked him as a President.
Shrub (elected in 2000) I did not vote for him, but am chagrined to confess that I considered doing so. I like him much, much, much, much less than when he was first elected. Needless to say, I will be voting for Kerry this fall.
My record of how I feel about Presidents after their first term is mixed and is pretty independent from party affiliation. The fact that I despise Bush right now is based exclusively on his behavior and has nothing to do with my prior voting tendencies.