How can I contact the makers of the Sims games?

Just email them at support@ea.com. Better yet write out all you can think of for the future game. make a copy of it in print and digital then mail it to yourself, don't open the package then contact them with your ideas. Then if they make the game you described to them without giving you funds or credit you can prove you came out with it first. I knew a writer who sued another writer for stealing her work and won the case with the proof she had mailed to herself.