Brad Garrett (now an Emmy-winner for "Everybody Loves Raymond") really pulled this off superbly. Judging from the wealth of mannerisms, tics, vocal inflections, attitudes, and body language, it would seem that he made a careful study of Jackie Gleason in the various stages of his life. The hard work paid off in a vivid characterization that really brought the man to life without any cartoon-like exaggerations. The rest of the cast were uniformly good, but if Garrett hadn't managed as well as he did, it would hardly have mattered.
The writing, direction, and cinematography were above average for a TV movie, in my opinion, and I didn't really find the three-level flashbacks all that confusing. As an earlier commentator said, this was a long, turbulent, and wide-ranging life, and the three levels of flashback were an effective way of touching on several different stages of Gleason's life without expanding it to miniseries length.
I too was interested to see if any of Gleason's movie work would be portrayed, as I have fond memories of "Soldier in the Rain," "The Hustler," "Requiem for a Heavyweight," and that strange film where he tried to do a Chaplinesque turn as a mute simpleton, "Gigot." I'm guessing that in the interest of keeping it under two hours, and in consideration of the fact that most people see Gleason as a TV star first and foremost, that part of the story was jettisoned. It would have been interesting, though.
Before having seen it, I'd read some statements cautioning avid "Honeymooners" fans that they might be annoyed with the recreations in this film. I can see what they were talking about, in that several scenes from the show about Ralph getting a TV set were smooshed together into a single scene. While it managed to get the most memorable lines from the show together in a single compact scene, it could be a bit off-putting to those who know the shows so well that they've memorized the scripts (that's me, I'm afraid). The overall excellence of the production, and Garrett's outstanding performance, made this a forgivable sin for me.
Gleason's personality is not shown in a particularly good light in this piece. He is portrayed as being insecure, egocentric, petty, tyrannical, abrasive, possessive, and yet aloof from even his closest friends and colleagues. From everything I've read about the man, that's pretty much true. I still love Gleason and the expansive, lovable, down-to-earth everyman character he created for himself, even if I know it's not really true, but it tends to confirm my suspicion that it's always best to worship your heroes from afar.