You could always try UA690 which leaves an hour later. Of course at 38% reliability it's only slightly better.

The problem is not airline/departure city specific. NW1190 has a 17% reliability from DTW to LGA. The Northeast corridor is seriously over impacted. Add to that the fact that AA360 arrives in that 6 to 7 pm LGA peak arrival time and you end up with 25% ontime reliability.

Don't expect this to get any better until the FAA forces the airlines to reduce their flying schedule into the area.