While the F-22's primary mission is air superiority, it also has an attack capability using bombs stored internally. Basically, it can go after the same kind of targets that you'd send an F-117A after, only it can do a lot more. The F-117A represents 1st (or 2nd, depending on whether you count the SR-71 as 1st) generation stealth technology. The B-2A has more refined stealth with fewer compromises to the aerodynamics than the F-117A. The F-22 is the next generation. It reportedly isn't quite as stealthy as a B-2 but has capabilities no other figher or bomber possesses. But the damned thing is very expensive, which will limit the numbers eventually built.

The F-15 is was designed in the late 1960s and early 1970s. It's a hell of a plane and the systems have been updated several times. However, from certain aspects, it has the radar cross section of Mt. Rushmore (literally). While it'll likely remain in service for another 10 years or so (in the USAF, perhaps longer in other countries), it's days are numbered. Tactical aircraft without stealth have a limited future.

The F-22 has been in development for nearly 25 years, a figure that probably has the late great Lockheed engineer Kelly Johnson spinning in his grave. However, it was the avionics and related systems more than anything else that took so long (and so much) to develop. The systems have capabilities that are only beginning to be explored.

I still wish it didn't cost so damned much.