Well, speaking as a James Marsters fan, I have to admit my first reaction to this is to smile and shake my head, but what the Hell, let's assume you're actually serious, and search the post for anything like crediblility, just in case you do really want to be taken seriously.
First of all I have to say this practice of presenting outrageous statements as accepted fact without any kind of support is what makes me suspect you're just joking.
For example when you say, "Denisof and Head are considered the best actors on both shows", it isn't that I don't agree with you, but I've never seen any kind of general consensus on this matter. If you were to post a poll on this, I'm not sure you would get the results you're hoping for. So how can you state it as fact, when there's no evidence to support it.
I agree with Cordelia when she says you should clarify the initials. When you said AH I assumed you meant Alyson Hannigan. Saying there's no chemistry there would of course be ludicrous. Xander says you mean Andy Hallet, so I'm going to now assume that's who you mean.
I also agree with Xander when he says you can't come to a conclusion of a lack of chemistry based on one minor scene as with Denisof, or the lack of scenes as with Hallet.
But speaking for myself now, I don't know what you saw in that Spike/Wesley scene from Numero Cinqo that allows you to suggest a lack of chemistry anyway. I thought it was pretty good.
This is the one you're talking about, right?
WESLEY
(over his shoulder)
I wasn't aware that you could read Cuauhtitlan pictograms.
SPIKE
(pan over to show Spike standing behind Wesley)
Who, me? Nah, I was just... is this one of those books on prophecies?
WESLEY
No, it's a source book. Each one ties into a discipline within the Wolfram & Hart archives. This one is linked to historical narratives.
(points to another book lying on a table)
That's the one dedicated to prophecies.
SPIKE
(walks over to the book table)
So...you could look up that, uh... sans shoes thingamabob. You know, the prophecy that says that Angel gets to be a real boy again.
WESLEY
Shanshu prophecy, yes. Uh, though it's a bit more complicated than that.
SPIKE
Complicated.
WESLEY
It tells of an epic, apocalyptic battle and a vampire with a soul who plays a major role in that battle. And there's the suggestion that the vampire will get to live again.
SPIKE
When you say, "plays a major role in an apocalyptic battle," you mean like, um...
(trying to be casual)
heroically closing a hellmouth that was about to destroy the world?
WESLEY
The text isn't specific about the battle.
SPIKE
But it's specific about the name of the vampire with a soul.
WESLEY
No, I imagine it could be any vampire with a soul...
(looks at Spike)
...who isn't a ghost.
SPIKE
(scoffs)
It's a bunch of nonsense. It's a bedtime story to get vampires to play nice.
WESLEY
(looks back at his book)
Says you.
SPIKE
No, says Angel.
(Wesley looks up)
Yeah. Tall-dark-and-dreary told me he doesn't believe in that Shanshu bugaboo. Says it's a sucker's game.