You really have absolutely no idea on this subject hovz. Why even comment on something if you can't even be bothered to read a review? Or at least read some of the comments on this very forum.
First Resident Evil 1 and 4
Res Evil 1 has pre-rendered backgrounds, Res Evil 4 has all realtime graphics.
Res Evil 1 has a fixed camera, Res Evil 4 has a proper camera with control over your own view.
Res Evil 1 has no real aiming, just bottom, middle and top (aim at feet, stomach or head). Res Evil 4 has full precision aiming so you can fire anywhere you want.
Res Evil 1 has fairly simple enemy reactions, that's all that's needed since you can only fire in 3 area's. Res Evil 4's enemies react differently depending where you hit them. Shoot them in the foot and they'll fall and be crippled. Hit them in the shoulder and they'll grab the wounded shoulder, hit them in the knee and they'll limp, and so on.
Not to mention stuff like no zombie's, no umbrella corporation, no t-virus ect ect. Res Evil 1 is a standard clunky RE survival horror (a good one but standard stuff for the series never the less). Res Evil 4 is a third person action-survival horror. New camera view, new enemies, new gameplay, new weapons and more. They are actually quite different games!
Now Resident Evil and Eternal Darkness:
Eternal Darkness has full and easy control over the movement of the character so you can go in any direction just by pressing that direction on the stick. Nothing like Res Evil 1's controls which are based on turning with left and right and walking forward with up.
Eternal Darkness allows sword fights and is very focused on magic attacks as well as guns, again nothing like Resident Evil 1 which is just about guns. I'm not even going to bother continuing. Basically it would be quicker for me to list the similarities between the games since there are so few.
Either read some reviews of these games (or even better play them) or just stop posting.