Where?
We would be no-where, lol. What if dinosaurs stayed alive, we couldn't get big enough with out em eating us. It would be hell, u get born, and killed in 5 minutes! lol

I doubt we would exist had dinosaurs survived. The KT event killed off all the dinosaurs, and also made the Earth perfect for the mammals, which would soon evolve into our modern mammals today. Some dinosaurs survived, becoming reptiles and birds, but most died out. Even if we did somehow manage to evolve, we would be drastically different. I doubt we would be little more than slightly intelligent food for mega-predators.

There's another theory that suggests that if we had developed alongside them we'd be eating them instead of cattle, or using them to war with each other such as the old cartoon Dino-Riders.

Lol.

Yes but when the dinosaurs reigned, mammals had to be small in order to avoid being lunch for huge dinosaurs. Mammal predators use intelligence and tactic (like hunting in packs), dinosaurs used pure force and intimidation; that's why they were so big.