I actually like the tonal shifts, as you call them. I think they can all fit inside a fun package. For example, look at the Princess Bride. The film has romance, goofy silliness, drama, comedy, action, etc. One minute the hero is comically rolling down a hill, shouting about his undying love and then fights silly giant rats and the next Inigo is confronting the six-fingered man who killed his father in an emotionally impactful scene.
I like that Gears has the range to go from Rambo bro-action, mowing down 30-foot spider monsters, to Dom's emotional discovery of Maria. (I don't like how Dom killed her, that was evil, imo. Years later Cliffy B said it was his commentary on the whole Terri Schiavo scandal [a woman who was starved to death]. I fundamentally disagree with Cliff's views on end of life issues, apparently.)