the F-15 is slightly faster than the F-111 (Mach 2.5 for the -111 and either 2.6 or 2.7 for the F-15)
Looking at figures in such a manner doesn't give any indication as to a particular aircrafts capability. Yes, a F-111 will do 2.5M, but only above 50,000 feet, decreasing linearly to 1.2M at sea level. The F-18E/F 2.0M above 35,000 feet decreasing linearly to 1.1M at sea level. Then those numbers are for basic aircraft which change with aircraft configuration, it takes real in depth analysis to gauge which aircraft is the better for the mission you desire it to fly.