Here are some points I picked up from analysing different genres of film and game.
Tension and music build up can suggest a horror aspect. Jump scares are also a giveaway of a horror genre. Weather is often used as an indication of horror, particularly dark skies, thunder and lightning, and rain.
Landscapes that seem otherworldly are good evidence for a sci-fi genre. Strange creatures also indicate this.
Action Fantasy Game
Dragons show an obvious fantasy element. Weapons and buildings built in a specific older style suggest that the game is probably set within the 10-16 century and that the game is packed with action and death. This all ties into Action Fantasy.