Halo set the pattern for how to do FPS on consoles. Metal Gear was just a series heralded as brilliant. It, however, hasn't set a template for stealth titles alone. People don't talk about Metal Gear Solid killers, but they say Halo killers. A major reason probably is that FPS is far more of a popular genre than stealth. One could say the movie-like feel of MGS is influential, but LONG LONG LONG cutscenes are NOT the norm.
One can argue Grand Theft Auto is also more influential than MGS. Now, is MGS influential? Yes it is, but not nearly as much as other games.







