15 second 4 bangers aren't rare and still not what I consider quick.
IMO once you're getting along in the 14 second 1/4 mile range you're starting to be quick,13s your company is getting rarer especially with a 4 banger and those are generally FI'd from the factory. If you run 12s your company shrinks considerably and even the quickest 4 bangers need some outside help to get into the 12s.
'12 Focus Red Candy SE Sport 5 spd
'99 Toyota 4Runner Sport
'11 Subaru WRX STI Hatch