Alright, I'll bite...
First off, let me say I'm writing this as someone that has enjoyed both AC and GTAIV. Just by your comments, I'd be willing to bet you probably didn't enjoy any of the GTA's. So your "facts based blow by blow comparison and discussion" seems a bit tainted from the get go.
Story:
AC: At first after finding out that the game was really revolving around a sci-fi story, I was disappointed. I didn't think it needed it, and couldn't possibly imagine how it could of helped the story. After playing it though, I thought it was well done. Not to mention the potential to now take the story into just about any generation they want. I think it really makes sense in the end.
GTA4: I don't think anyone can really argue that it's not just more of the same. However, I do think that when comparing them to previous GTA's these characters quite a bit more interesting and personally think there are a couple a gems in Brucie and Roman. I'm only around 55% complete though and from the spoilers and reactions I've read, it sounds like it really goes downhill from here.
When comparing the overall stories, I think the edge has to go to AC. However, if you are comparing how the stories unfolded I think the edge goes to GTA. AC's story was for the most part hashed out by the 3rd Assassination (been awhile since I've played it). Every assassination not only seemed the same, but even the dialogs they gave you for "clues" where damn near identical.
GFX:
AC: One of the best looking games this generation period. It was downright stunning on some occasions.
GTA4: I really don't think it's as ugly as most people make it. It does look really bad at times, but I think that has a lot to do with what they've done with the lighting and shadows. In my mind it's excusable. The real problem I have in the graphics department is the pop ups or pop ins (whatever they are called). In the parts of the city were you are actually able to pick up some speed and weave through traffic, you will almost always eventually get bit by some construction, curb, tree, or even car that just appears out of no where. To me that is pretty damn inexcusable for a game that is supposed to be as much about going around this vast city as it is the story.
Sound:
AC: Nothing really stuck out for me as "amazing context sensitive music." Again, it has been awhile so I could just be forgetting. I do remember hearing the same damn "conversations" coming from the vendors, beggars, and people milling around the cities. I mean each character was limited to what MAYBE 4 different things they said. I mean hell, they could have at least changed them up from city to city. You have to admit that was downright annoying.
GTA4: I think the guns sound better then previous versions. I personally like the whole radio station aspect. I think they are pretty weak this time around though. Overall, GTA's sound is whether it's your cup o' tea or not. There is nothing deplorable about it technically.
Gameplay:
AC: The combat was just down right fun. I don't think it was as groundbreaking as they wanted it to seem during the hype phase (with the buttons controller each hand/foot), but the animations were plentiful enough to make a fun ride. I do think it was a bit on the easy side though, but fun none the less. Climbing was no challenge what so ever, but once you started getting into chases it was pretty evident that was the only way to go with it. I do hope that the next game will have a couple more challenges in figuring out how to climb to a certain points though. The side missions need a lot of work though, I have a hard time believing anyone could get halfway through this game and not get sick of them. Especially if you were trying to get all the eagle points and info gathering before each assassination.
GTA4: Again, it's really more of the same. If you liked previous versions, you'll like this one. The shooting was the best it's ever been, but still very subpar if comparing it to other shooters. As well documented, the driving was a joke. I'm in the crowd of people that say it's not so much the driving all around, it's the inconsistency that is annoying. The randomness of getting thrown from the car, or the clown like suspension on some curbs, but not others.
Overall:
I'll judge them both by how I judge most things that I buy for entertainment..."Did I get my money's worth?"
AC: I would say that even though 1/2 way through the game I just wanted it to end (because of the repetitive nature), I definitely felt that I got my money's worth even if it was more in an investment sort of way. I felt like this was a game that tried to do things that others have not, and it was a bit incomplete. However, if my purchase helped with getting a sequel out, I'm definitely happy.
GTA4: I'm only halfway through, and I've felt like I've already got my money's worth. The flaws are not game breaking for me, but if not cleaned up by the next installment I'll be disappointed. I'm having a hard time deciding where to rank it in the series, but I've yet to feel as if I just want it to be over. Hopefully the last half won't change my mind!
