In my experience, Fishing is the fastest skill to SuperMax. Inventing probably takes the most time. I don't consider Photography in that at all, simply because it was nearly impossible to SuperMax in a normal lifetime, even before it was bugged.
I can't help but agree with you on this, Hosfac. Fishing is the natural, easiest supermax for an Immortal Dynasty founder. Gardening comes close second, but it still can't beat the "one challenge less" of the former.
I always avoid Inventing as a supermax. I like to do it as "other maxed skill" for my Logic/Handiness-oriented Immortal, as it simply suits the character.
If anyone wants, here is a plan for an official Dynasty.
# SuperMax skill/Career
1) Fishing/Science career
2) Painting/Painter career
3) Athletic/Professional Sports or Criminal (Thief)
4) Logic/Medical
5) Charisma/Politics*
6) Writing/Writer**
7) Handiness/Military
8 ) Nectar Making/Nectar Maker
* Even though that 100 joke challenge is a pain, Charisma is one of the easier skills to supermax.
** I know that watching a Sim type may make you go "zzz", but there are some nifty tips... though "zzz" will still be there.