It's nothing fashionable about it. I've seen it and it's bad. The writing is bad, the artwork is bad, and it's clearly created by people who have no respect for what Megaman should be. That's how I feel about it. I look at it and I see a betrayal of the spirit of the series. I think people just cling to it because it's the only animated series to represent classic Megaman.
Really, you'd be hard pressed to find a Zelda fan who loves the old Zelda cartoons, so I don't see why liking Ruby Spears Megaman is somehow sacred to parts of the fandom. Most fans of Batman turn away in disgust from the 1960's series, and you'd be hard pressed to find a Fantastic Four fan who'd defend the "The Thing" cartoon. I mean if it's just your tastes in animation, I don't see why, but you're entitled to that, but there's no reason to cling to it just because you want to be a bigger fan of Megaman.
Just my two cents on the matter.
All that having been said, it was Capcom of Japan's decision to handle the Megaman cartoon the way it was, and the only major difference between the pilot episode and the final product was the art style.
Also, from the back of my DVD case:
Executive Producer: Kenzo Tsujimoto (CEO of Capcom Japan)
Producers: Akio Sakai (President of Imagin Co., Ltd of Japan), Jun Aida (President of Square Pictures, Japan)
Supervising Producer: Toshihiko Sato (Founder of Production Reed Co., Ltd of Japan), alongside Ruby and Spears
Animation Directors: Hiroyuki Yokoyama (worked on a few of the MS Gundam series), Kenichiro Watanabe (directed such animes as Azumanga Daioh, Power Stone, Rurouni Kenshin, and the Galaxy Adventures of Oz), Minoru Okazaki (directed Dragonball, Dragonball Z, Dragonball GT, some of the Dragonball movies, and did storyboards for Lupin III and New Gigantor)
Production Coordinators: Hazuki Kataoka, Eiichi Takahashi
Background Design: Yoshimi Umino (Good LORD did this person do art production in a lot of anime, including .Hack, Arc the Lad, The Galaxy Railways, Zeiram the Animation, Candidate for Goddess, Ranma 1/2, Record of Lodoss War, and Tenchi Muyo)
The Megaman cartoon was
very much a Japanese production, and the only reason the animation style was changed was because test markets responded better to the more "American" look. Scooby-Dooified Rush aside,
not much else changed.