all games are not created equal

We knew this one was coming :P

Most everyone gets the idea of RE4 by now.  It was a major departure from previous games by including an over the shoulder camera (FINALLY), and putting much more emphasis on the action rather than horror.  The game still used "tank" controls, which meant the up and down moved the character forward and backward, and just pressing left or right made him turn in place.  Also, brandishing your weapon (whether it be a knife or a firearm) planted your feet firmly in the ground.

Well, here's RE5 and not much has changed in that respect.  As I play, not once did I feel fear.  There's certainly moments of anticipation and adrenaline, especially when dealing with chainsaw-wielding baddies (who can kill you with one slice, as it should be).  Other than a major environment change (RE4 was in Spain, RE5 is in Africa), RE5 only has one very tiny difference.  Co-op.
Ok.... thats a huge difference.  Two people, either locally or online, can play through the entire campaign from beginning to end.  It's not even fair to call it a single-player campaign, cause even without a buddy, you have an AI controlled partner instead. 
"Player Two", as it were, controls Sheva, who reminds me of Farah from the recent Prince of Persia trilogy.  She's very reasonable, not annoying, and doesn't try to add too much sexy to the game, which is always refreshing (and very much a departure from Ada in RE4).  However, my gripes with her (and tends to be the case with most AI controlled partners in similar games) is that she gets a little happy on the healing items.  I'm one of those people that like to wait til I'm on the brink of death before applying some first aid.  But oh well.

Enemies in these games are mostly similar, especially in with the basic zombie-esque enemies.  Many seem to very much be a copy-paste job going from RE4 to RE5, though RE5 does throw in a couple surprises, including random fat guys that soak up tons of damage.  Also, expect to die from gators.
Weapons so far seem to be pretty much the same.  You got your handguns, rifles, shotguns, grenade launchers, etc.  However there doesn't seem to be as much of a selection for each weapon type in RE5, which is fine by me.  While I miss the merchant from RE4 (Welcome! *flash* ), RE5 does let you upgrade and buy weapons and few items between chapters.

One thing that makes item management a little confusing in RE5 comes to playing online.  In RE5, Chris and Sheva each have 9 slots to put items in, not counting infinite space for key items and treasure.  What is a little strange is where all these items come from.  When someone joins your game, they bring with them all the items that they currently have in their own game.  What this means is that when you play online with someone that has progressed farther than you, they will have much more powerful weapons and items than you.  However once they leave, any items that they grabbed along the way goes with them.
*EDIT*
I just read that on the 360 version, this is even more confusing when player 2 joins in using their own profile on the 360.  Apparently, all the items that are picked up stay with the profile that the player is using while playing.  Weird.

I think overall I preferred the environment of RE4 more.  The village, castle, and island were all very interesting.  RE5 also has a village and a mine, but also includes a marsh and a labyrinth.  They are all great to look at, but overall I wasn't terribly impressed with the level design.

I haven't checked out Mercenaries in RE5 yet, so I can't judge on that.  However so far, minus the co-op, RE5 is just RE4 again, which isn't a bad thing, really.  RE5 just barely edges out for me.