going back to the original question, as Dave Roof correctly points out that the F-18 is more versatile than the F-15, but the F-15 is by way & far the more capable than the F-18.
With regards to the F-18 being more available & flexible as it is on a mobile airfield - this is only true if the mobile airfield is in the correct place at the correct time!
I say in an ideal world - stuff versatility!!! Versatility is what has taken us from a carrier deck covered with such airborne miracles as the F-4, F-8, F-14, A-4, A-6, A-7, EA-6B, RA-5C, S-3 & a couple of twin props........... to the F-18 & a couple of twin props - as an aircraft lover I know which I would choose (ideal world, budgets aside).
Where as most of us have had the luxury of being able to see, hear & read about all these amazing aircraft while still a reality, future generations are going to have to suffer the massacre & watch a couple of "versatile" A/C. Give it a few decades & the variation of combat aircraft in our skies is going to be an F-18/F-35 alike, the US only F-22, a possible a euro consortium multirole, possible a couple of Russian multiroles, possibly a multirole Swede & possibly a multirole from China (not that anyone will see it) - that is 3 > 7 hardcore combat A/C (go back a few decades & there was more variation on the average US carrier deck)? At the moment we have the luxury of having a few overdue for retirement "oldies" still flying, but the continual upgrades wont allow them to resist the gate guard post forever.
Versatility = bad day for the A/C enthusiast = more profit for the A/C manufacturer (how many are left).
Bondo - correct on the EE lightning, supercruise in service 46 years before the "holy grail"!