Taxi is generally fastest but consider the train. NJ Transit runs trains from Secaucus to Meadowlands starting about 3 hours prior to kickoff. Take any NJ Transit train from Penn Station to Secaucus and then go down to the lower level for the train to the Meadowlands, fare is $5.25 from Penn Station. You can take a taxi from JFK to Penn Station, fare is $45+tolls+tip, starting at 7am you can take the NYAS express bus from terminal to Penn Station or AirTrain from terminal to Jamaica Station and either LIRR or E subway to Penn Station, trains run 24/7. Games generally run 3-3.5 hours. See www.njtransit.com for schedules and info for game day service.
Taxi is generally fastest