for me the best points per min ratio is probably doing gauss spamming against unprepared people. you get 3000-6000 points in 15 min. (ratio=200-400)
a good rush gets my around 1500-2000 for 5-10 min but often its like 300 for 5 min (ratio=150-400 very rare)
a good turtle medium length game is 5000-8000 for 30 min (ratio=170-270)
a good very long game is 5000-12000 for 60 min (ratio=80-200)
turtling until the guy quits is 33600 for 120 min (ratio=360)
deathmatch 3000-5000 for 20 min (150-250)
so gauss spamming is the best way to get points!
I get banned for no reason