Don't the 1960s hold the record for mass entries - about 9 works Fords and 7 Ferraris. Then in the late 1980s, you had 5 Jaguars, 3 Porsches, 3 Toyotas, 5 Nissans, and 3 Mazdas in GTP. The Sauber Mercs would show up occasionally too.
These were the best years and it looks like we're heading that way now.