There's a difference between what is most important and what is most fun. Air-to-air is the most fun - I mean, you engage other supersonic enemies in a battle where all the players have all freedoms of movement. On the other hand, air-to-ground has been the primary purpose of airpower almost since its inception. When airplanes were first invented and applied for military use, they were initially as recce platforms, but then some guy saw the usefulness of using airpower as long-range artillery and that role has stuck with the military airplane ever since.
However, A/G is arguably not as "fun" - you're attacking targets who are limited to movement on surfaces, with much less mobility than your own airplane, if mobile at all. There's no style or finesse required to kill the target, and a mud-mover doesn't need the golden hands of a fighter jock to become an ace at what he does. I guess metaphorically, fighter pilots are the quarterbacks, the receivers, the running backs, while strikers are the linemen.
So, the question boils down to whether you wanna be the star quarterback, or the fat linemen?