Not particularly related to the topic but when will I ever post about FM11 again, right?
I've bought every FM apart from 16 and I'm still playing FM11. I started with a mediocre PC so I'm only running 3 countries (Holland, Germany & Belgium) but I'm controlling 11 club sides and 4 national teams. The longevity comes from reinventing the game for myself (and using FMRTE to modify things like a wonderkid goalkeeper who's only 5 foot 3 inches tall). Never made a team super rich by editing, sold to buy only.
For example, I could win 7/9 titles with Ajax but try my hardest to turn VVV Venlo & ADO Den Haag into top 4 sides and progress from there, that more often than not turns in to a relegation battle which is actually more enjoyable. Moenchengladbach were fighting a relegation battle in the third division, so this is my next project. Players who wouldn't get anywhere near Ajax/Dortmund reserve team could make a massive difference to them, which is also fun. Two of my teams, Hertha Berlin & Wolfsbug, battled it out for the title last season, which certainly kept me interested more than Bayern, Dortmund or Stuttgart did.
I'm sure that I could have done similar things on FM12-15, but I've invested so many hours into this save that I keep going back. Whatever difference the tactics make on more recent versions doesn't matter to me, I enjoy FM11 more than the others, despite the improvements. 2010 was a good year for sports games in general imo, although I couldn't go back to Madden, MLB etc as much as FM.