Simulation is such a vague term for a game genre. It can be applied to anything - Tekken could be a fighting simulation. Fifa 2004 could be called a soccer simulation.
The general meaning of simulation in computer games is for games that emulate a system but cannot be defined under conventional gaming genres - ie racing. They tend to include genre types like "god games" or "management games".
Gran Tourismo is predominantly a racing game, but involves realistic customizations and driving schools and all that, so can probably fall under the management genre, I suppose.
Games such as Themepark, Simcity, Simant, Railroad Tycoon are "Simulation" games, in the videogames meaning of the word.
Anyway I voted for simulations because I'm a fan of the 4 games above