All high speed supersonic inlets are designed to control and shape the shock waves.
Slower supersonic aircraft -- like the F-16, have a pitot inlet. This forms a single normal shock in front of the inlet.
As you go faster, you use multiple shocks (the final shock is always a normal shock). First, one external oblique shock followed by the normal. This is an external compression inlet.
Then, you go to multiple external shocks before the normal.
Then, you use both external and internal shocks. This is a mixed compression inlet.
Each of these stages has an increase in complexity. In order to get these inlets to work across a range of Mach numbers, they need a series of movable ramps that must be controlled. They often involve boundary layer suction to prevent massive separation in the inlet. Consequently, increasing the top speed required of the aircraft drives complexity and cost of the inlet system.
When designing the shock system, you can have a 2D system or an axisymmetric system. The 2D system uses 2D oblique shocks (ramps) to form the inlet -- this is what you see in a F-15, F-14, and most of the aircraft you mention. The axisymmetric system uses conical shocks to form the inlet.
For the most part, you can achieve similar performance with a 2D or axisymmetric system. The choice is more about how it integrates with the rest of the aircraft.
The axisymmetric system has less design freedom -- for example, you can't tuck an axisymmetric inlet under a wing.
The design of the latest generation of fighters is dominated by stealth considerations -- so if you're asking why they look different from previous generations, the answer is almost always stealth.
It would seem that integrating a 2D inlet into a stealthy configuration is easier than doing so with an axisymmetric inlet.