SWOS4EVA...
For me... the Sensi series is king, with SWOS being the ultimate - excellent playability, easy to pick up, hard to master, have a 20 year career as player/manager, and the sheer number of teams...still blows me away. In fact, I remember first starting SWOS, and finding a little local team in New Zealand near where I live was included!
(granted, the name was spelt wrong, and the team no longer exits, but respect for the effort!) Obviously, the Amiga version was my preffered system, but I liked the PC versions too.
A close second for me is Goal! and the KO series. On other platforms, I've played one of the early ISS games on PC which was pretty good, some of the FIFA games on MegaDrive, and Total Football on the MegaDrive was pretty decent, (had it on Amiga too)...
I've also liked some of the PES series, on Xbox and PS2...but SWOS still beats them all!