Gamehead, I didn't quite finish RE4, but I did put in about 6 hours into it. The only thing I think those combat systems had was the perfected camera. Dead Space had several more tweaks than limb removal. The weapons were incredibly diverse, some were kind of bizarre (ripper). Weapons like the flamethrower, contact beam, force gun, and mine laser, plus all the alternate firing modes made combat very interesting and incredibly fun all the time. RE4 had pretty boring weapons in comparison. Also, stasis and telekinesis have been done before in other games (Psi Ops, Fable II), but it was pretty exceptional in Dead Space. They did straight up jack the post-mortem mutations, where tentacles go flailing out of the recently decapitated.
I see what you're saying, but I don't agree with you, except for that part about how everyone should buy it.