well, not all of it should stay horror. i mean, in terms of plot, this should be in "climax" or "conclusion", that's where it all action uprising. also, it isn't weird if a story from the prologue until epilogue it's stay slow and horror? it's like it has no pulse, it's static. i mean, "what if" from the moment Chris was introduced, until now he's still in awe, still afraid with all the enemies he encountered (zombies, Tyrant, etc.)
Resident Evil plot should look as a whole from the first RE game until RE6. unlike Silent Hill tho, each game has it's own plot that not really related to other games, except for Silent Hill Origins, 1 and 3.