Let us say that the modern era of American politics began in 1965.
Since then, there have been seven midterm elections coming after the election of a new President. Let's consider them.
1966 -- Johnson (D) takes a bath as conservatives rebound from the disaster of 1964. Loses 3 seats in the Senate and 48 in the House.
1970 -- Nixon (R) does okay, gaining a seat in the Senate and losing 12 in the House.
1978 -- Carter (D) loses 3 Senate and 15 House
1982 -- Reagan (R) loses 26 House but none in the Senate
1990 -- Bush (R) very modest losses, one Senate and 8 House
1994 -- Clinton (D) gets brutally hammered, 8 Senate and 54 (!) House.
2002 -- Bush (R) becomes the first President in almost 70 years to make gains in a midterm, picking up 2 Senate and 8 House seats.
Let us say that a Senate seat is worth four points and a House seat, one. (Yes, yes. And a real methodology would include governors and state legislatures as well. Toy model, bear with me.) How do they rank?