Just reading the comments, I don't think Gill, God Rugal or Magaki are that hard. Granted, they beat the bloody crap out of me many a time, but after a while they were still beatable. Hell, I've beat Gill and Magaki with all characters/teams just so I could see their endings in the arcades. (Granted, I had the Japanese versions at home so I could practice, but I still wanted to see the endings in English.)
I think the main reason Moz is having such a hard-time with God Rugal is how insanely rush-crazy his play style is. You gotta play defense on God Rugal. I usually use characters that have counters, like Yamazaki and Rock, and counters f'en hurt. Even if you don't have a command counter, wait for G.Rugal to throw a projectile and miss a Gensai Cutter. (I also use N-Groove, which makes dodging moves a hell of a lot easier.)
As for Magaki, it's simply a matter of have your most powerful physical attacker fight first to soften him up, then after you've got a lot of Super built up, switch to your leader and start Super Canceling/Dream Canceling like crazy. Again, with most SNK style bosses, you've gotta be reactionary. It's a lot harder for Magaki to block a super when he's in the middle of a move that whiffed; his 'across the room' grab saved my ass plenty of times. It also helps to know when to block high or low when he starts using that phantom fireball shit.
I can't remember exactly how I beat SFIII with every character. Last time I pulled out the DC and played through, I died a few times to him, but it still only took 15 minutes at best.
The only boss that made me completely give up on beating it was Mildred Avalon from Arcana Heart. It's like she has God Armor. No matter how many times I got so close to killing her, she'd unleash that super death-beam that would take off half my life even if I blocked it. At that point (actually, after reaching that point about 10-15 times and failing, because I'm thick), I just gave up. Even if I do that crap that makes sure she doesn't start the match with 9 full power bars (can't remember exactly what I had to do, I just remember having to do that), she'll still somehow get two power bars during the match and chain a "Half-my-life beam" into a "Half-my-life beam", killing me instantly.
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