So basically what I do is skip a year. Because every year you're looking at about a handful of changes to the gameplay, and maybe one or two tweaks to graphics. Like from Madden 25 to Madden 16, you can tell the crowd's graphics, stadium graphics, player models and sideline graphics are improved drastically. But going from Madden 15 to Madden 16, it basically looks like the same game. If you go from Madden 15 to Madden 17, that's when you'll see a difference easily. And not just the graphics, but I'm talking gameplay too. Madden 13 didn't allow you to edit rosters (iirc, I could be wrong, but there was one Madden that you couldn't edit the roster), but in Madden 16 there's all kinds of freedom with editing rosters, to being the owner of the team and making trades, etc.
And so what I've noticed is that if you skip an iteration, the next one will take all of the good things from the past say two or three iterations to make the next one. That's when you'll be impressed. I'm not about to shell out $60 for some touchdown celebrations, running physics, and ball physics lololol. Anyone who does that are just idiots. But I'm not gonna fault them for it, because they love the game. I can't tell someone not to buy something they love. So power to you if you're willing to shell out the cash for some basic upgrades. But to those not willing to do so, just skip an iteration and stop bitching.