I'm surprised there are no choices for 1982, 1977, and 1974. For the veteran chasers, these were fantastic years in the Plains. 1982 had a number of special events in the TX Panhandle, plus the Altus tornado. The "Seven Days of May" in 1977 brings back many memories for some veterans. 1974 had a number of events, including the 6/8/74 Central OK outbreak.
I began active chasing in the Plains in 1987, and by far, my best year was 1991. It seemed that for every severe weather outbreak, you could not buy a bust. There was something magic in the air that year - if there was a chance of severe weather, there was a going to be a photogenic storm/tornado somewhere. 3/21, 3/26, 4/2, 4/12, 4/26, 5/10, 5/11 (see avatar), 5/15, 5/16, 5/26 were tremendous (I probably forgot some). A "Storms of 1991" would have had to take up at least two full-length DVDs (one just for 4/26 alone).
Believe it or not, I saw my highest number of tornado days in 1992. But I would rank it "in the middle" since many were not photogenic and/or short lived.