The best cardio is the one you do on a regular basis…period.
Having said that there are forms of cardio that burn more calories than others like swimming and the stair master. Now if you can't get to a body of H2O or have a stair master near you, the bike will have to do.
Extended time running is over-rated and unless you are genetically made to run, it can hurt your knees and back, more than squatting.
Fat-burning, on average, starts after 22 minutes of doing cardio so grab the remote and ride for an hour.
Good Luck!