I think it's difficult for most people to remember how dominant GM was for over sixty years. Here's a comparison to the top 10 sales in 1980 to 2015. GM went from 7 in the top ten to 1.
1980
1. Chevrolet Citation 374,706
2. Chevrolet Chevette 373,988
3. Ford Fairmont 285,272
4. Chevrolet Malibu 267,732
5. Chevy Impala/Caprice 261,819
6. Toyota Corolla 257,315
7. Ford Mustang 225,290
8. Oldsmobile Cutlass 210,784
9. Buick Regal 199,207
10.Volkswagen Rabbit 177,118
2015 (March)
#1 Ford F-Series 67,706
#2 Chevrolet Silverado 45,193
#3 Ram P/U 41,595
#4 Toyota Camry 40,800
#5 Toyota Corolla 35,532
#6 Nissan Altima 31,993
#7 Ford Fusion 29,044
#8 Hyundai Elantra 28,794
#9 Honda CR-V 27,618
#10 Nissan Rogue 27,418