To me, fighting games like Street Fighter, King of Fighter despite many series and changing of characters, they still the same. You choose characters, and play to defeat several characters and finally the boss or you simply play it with your friends just like FIFA & Pro Evolution Soccer
Racing games series usually don't differ from one to another. Other than the graphic, i don't see any much changes with Mario Kart
Sonic, Super mario, Megaman are the same adventure games . You still collecting rings, mushroom and walking until the end of stage to move on to next stage and defeat the mini boss before final boss.
Pokemon, despite different gens, you still doing the same thing, collection pokemon, defeat gym leaders eventhough their stories are different yet no significant changes in them.
The sims, you still create a family, house and buy things.
And people will of course said the same thing about RPG series. But here is the thing with RPG series, not only their characters are different, the story lines are different. Their bosses are different. The battle system often changes. Other kind of games series only have minor changes. RPG series on the other hands have very significant changes. That is why I only bother to vote 1 series for street fighter, The Sim, Mario, Mario Kart, Fire Emblem etc