Ktenshi:

1. Re: roles in team - IMO, Mamoru is clearly the Sixth Ranger, very literally. He has some trait of Chick, but IMO on the whole Usagi would be the Chick, dubbing as the Hero. And joing these roles by a heroine is very interesting. Mamoru doesn't seem to be comppletely integrated in the team to be the Chick.

2. Re: Mamoru as supporting character:

IMO the his being one of the main characters, not supporting ones, should not depend on whether he is a senshi or not. He is after all in five season, from the first episode, while the Outers in two, except for Sailor Pluto.

I'm very much in the dead author school of thought. Though anime doesn't consider him a senshi. As Sailor Crystals are replaced by True Star Seeds. (and Chibiusa in anime doesn't have True Star Seed though sshe is sailor senshi). There are also episode titles like "Ten senshi gather" (Inners, Outers + Chibiusa) or "The battle of ten senshi" (Inners, Rubeus + Black Moon Sisters). He isn't included as senshi, though he participates in these.

Though he clearly is on of Main characters and fighting doesn't matter.

I haven't read every post in this tread so far, but I would like to throw my two cents in. Mind the fact that he is literally my favorite, so I may be a little biased, but here are my thoughts:
I love Mamoru, even in the anime. 
**for the rest of this i'm only going to be talking about the anime**
One of the points I've seen brought up is that Mamoru is a jerk in the anime, and I have to disagree to a point. I don't know about Japanese culture very much, but I know that, personally, I'm a pretty sarcastic person. So, when I see Mamoru being a smartass in the first season, I don't see it as being mean, but more of him trying to be funny in his socially awkward way, and Usagi (a girl that's pretty and nice and has been socially coddled in her 14 years) doesn't react very well to it. I almost like this dynamic to their relationship because it's just...I feel like it gives both of them room to learn from each other. 
Anyway, so, Usagi doesn't react very well and she retorts back at him, and that get's him flared up and he retorts back so it's just...verbal tennis with these two and it's both of their faults. They both think the other needs to mature, and that they themselves are mature, and so it just adds a little depth to the verbal tennis. 
But even with this, there are points in the show where they made him a chibi, just to make him a chibi. Particularly with the filler episodes. It's episode 2 or 3 and he makes a fat joke at her, and that's not Mamoru, not at all. He may be sarcastic, and a socially awkward dork, but he would never make fun of a girls weight. He writes poetry for Christs' sake. He'd be that guy that, calls another guy in class out because they're making fun of a girls' weight. So when he does it again in SuperS, it upsets me. Actually, all of the fat jokes in SuperS make me mad, but w/e. I don't really blame that one on characterization, i blame it on the writing.
It's late, so I'll finish giving you all my Mamoru word vomit tomorrow, but um...meh. here. words. hopefully they make some sense.
   

I wish Mamoru was in high school instead of college in the anime. Then we would be able to see his cute school uniform and reading glasses.

I'm serious when I say this. In episode 1, when I first saw Usagi and Mamoru fight, I thought Oooh, they look cute together.


And that was before Tuxedo Mask showed up. I thought the teasing was cute. He would like to annoy her but not hurt her feelings like he did once in episode 13.

I would LOVE to see animated high school mamo. and reading glasses YES. Anime guys with glasses in general are hotties. xD

I always thought that tuxedo mask reminded me of batman...sort of.

I have to say that I feel like they've improved tuxedo mask. Now he actually has his own agenda. In the 90s anime he appears at the scene like batman and throws a rose. In crystal he was breaking into Naru's jewelry store but there happened to be a battle. He also told sailor moon to get her act together and stop crying. 

Mamoru now actually has a reason to be around. Old anime he was really just someone who bothered her and saved her. Now he has his whole quest to find the silver crystal all on his own.    


Also Let's face it....Mamoru in crystal is H-O-T!!!

I must have this song, how has this gem been hiding from me for so long?

I completely agree with OP.  I mean in the anime, don't know why the animators/writers for the show, forced him to "date" Rei.  I mean that just kind off weirded me out cause he is a college student(90s anime only), that is dating a 14-year old(pedophilia much?).  He also is super mean to Usagi(again, 90s anime only).  I love him in the manga/Crystal when he is so much involved with Usagi and actually befriends her.

In the anime their relationship is still very innocent. I always got the impression that Mamoru was very much aware of the age gap between them, but at the same time, they were destined to each other. I think it's just a matter of keeping things innocent and slow until she's older.

I could go on for centuries about my disdain for 90s anime Mamoru.
Growing up I never put too much thought into it, but once I'd read the manga for the first time, and re-watched the anime right after.... OH HELL!!! 

He is just completely butchered. He's portrayed as disinterested and useless. and it's completely untrue to his character in the manga, who is loving, and exhibits a good amount of power and usefulness.
Heck he has his own damn crystal for goodness sakes. 

Crystal has made me so happy with keeping Mamoru's character intact. 
He does get a lock of shtick... but sod it... I LOVE him