Wait a minute! Did you leave out 1980 on the Republican side? And let's not forget 1968.
Fact checker:
Since 1920...
1920 - 1932 - Republican (12 years) - Harding, Coolidge, Hoover
1932 - 1952 - Democrat (20 years) - Roosevelt, Truman
1952 - 1960 - Republican (8 years) - Eisenhower
1960 - 1968 - Democrat (8 years) - Kennedy, Johnson
1968 - 1976 - Republican (8 years) - Nixon, Ford
1976 - 1980 - Democrat (4 years) - Carter
1980 - 1992 - Republican (12 years) - Reagan, H.W. Bush
1992 - 2000 - Democrat (8 years) - Clinton
2000 - 2008 - Republican (8 years) - W. Bush
2008 - ???? - Democrat (2 years so far) - Obama
Quickly calculated to:
Democrat - 42 (that's if you include 2008 - 2010)
Republican - 48
So in actuality, the government, at least in terms of Presidents, the Republicans since 1920 have held more years in office than the Democrats.
It's only if you take it back to 1912 that Democrats start picking up the majority, adding 8 years:
50
48
However if you discount the 2008 election cycle (since we're still in the midst of it) then you come out with:
48
48
Meaning that Democrats & Republicans from 1912 - 2008 have equally held the Presidency. If you stretch it to a century: 1912 - 2012, then Democrats win by a small 4 years. So up until this point the country has given power to Republicans & Democrats quite equally.
Unless you were including the changeover in Congress, then you are correct since from 1960 until 1992 is a long Democratic Congress while many Republican Presidents come in and out of office.
It appears, in terms of Presidents, Americans favor a hardhearted warmongering leader instead of a softhearted whimpy leader. See Carter vs. Reagan for a microcosm of such a debate:
"Commander-in-chief" 1980 Carter Campaign - http://www.youtube.com/watch?v=FtUhn0n9eg4 (emphasizes his military experience & peace experience simultaneously)
"Peace through Strength" 1980 Reagan Campaign - http://www.youtube.com/watch?v=3Z0VQ4vFwPU
For equality's sake I'll put other campaign ads from 1980 here:
"Fearing Ronald Reagan" 1980 Carter Campaign - http://www.youtube.com/watch?v=YcNi5DoprK0
"Door Slam" 1980 Reagan Campaign - http://www.youtube.com/watch?v=aZHRz_-G748
"Peacemaker" 1980 Carter Campaign - http://www.youtube.com/watch?v=wLBZ_-pgA1g
"The Ayatollah Votes" 1980 "Democrats for Reagan" Campaign - http://www.youtube.com/watch?v=gLKMXnsxHZM
"Nancy Reagan" 1980 Reagan Campaign - http://www.youtube.com/watch?v=GvMYqYesCrA
"Reagan's Record" 1980 Reagan Campaign - http://www.youtube.com/watch?v=zQ4CCQRDxKo
"Democrats for Reagan" 1980 Reagan Campaign - http://www.youtube.com/watch?v=ErosyL95VqA
"Jimmy Carter for President" 1980 Carter Campaign - http://www.youtube.com/watch?v=l2vdvzMSKS8
"Re-Elect President Carter" 1980 Carter Campaign - http://www.youtube.com/watch?v=xmT0gIEpMY0
~*~*~*~
And just because I find it utterly ridiculous:
"The Bear" 1984 Reagan Campaign - http://www.youtube.com/watch?v=NpwdcmjBgNA
~Chas'88