True. Democrats were able to unseat GHWB, Gerald Ford, Hoover, Taft.
But Republicans were only able to take out Carter (You can go back further and talk about Harrison and Cleveland and Martin Van Buren, if you want, as well as Presidents who failed to win their party's nomination for a second term).
Ross Perot's independent campaign had a lot to do with GHWB's defeat. There's a lot of debate about whether Bush Sr. would or wouldn't have lost in a 2-candidate race.
I believe had it not been for Perot, GHWB would have won.