Ninjustu (in general)
1- Orochimaru/Hiruzen
2- Hiruzen/Orochimaru
3- Kabuto/Minato
4- Minato/Kabuto
5- Jiraiya
(all have shown skill in many areas of ninjutsu eg. sealing, space-time, medical etc.)
Medical ninjutsu
1- Tsunade
2- Shizune/Kabuto
3- Kabuto/Shizune
4- Sakura/Hashirama
5- Chiyo/Hashirama
(wasn't sure where to put Hashirama so yeh)
Elemental ninjutsu (in general)
1- Onoki (mastered 3 elements + kekkai touta)
2- Mei (mastered 3 elements + 2 kekkei genaki)
(No one really compares to these 2 imo)
Water
1 - Mei (I know the databook says Tobirama is the most skilled but for me, feats>hype and to me, she's shown the most skillful display for water style jutsu)
2- Tobirama
3- Kisame
4- Kabuto/Itachi
5- Kakashi/Zabuza
Fire
1- Madara
2- Sasuke/Itachi/Hiruzen
3- Jiraiya/Hanzo
Earth
1- Onoki
2- Kitsuchi/Jiraiya/Hiruzen
3- Kakashi/Akatsuchi
Lightning
1- Kakashi/Sasuke
2- Sasuke/Kakshi
3- 3rd Raikage
4- Darui
5- A
Wind
1- Naruto
2- Danzo
3- Temari
4- Baki (used an A-rank wind jutsu against Hayate - rank is to do with the difficulty of performing a jutsu)
5- Asuma
Sealing jutsu
1- Kushina/Mito
2- Minato
3- Jiraiya/Orochimaru/Hiruzen
Taijutsu
1- Gai
2- 3rd Raikage
3- Tsunade/A
4- A/Tsunade
5- Lee
Genjutsu
1- Itachi
2- Shisui
3- Kurenai
4- 2nd Mizukage
5- Hashirama/Tayuya
Speed
1- Minato
2- Naruto
3- A
4- Gai
5- Lee
***Hanzo's speed was said to be unsurpassed on water***
Stamina
1- Naruto
2- Hashirama
3- Madara
4- Killer Bee
5- Tsunade
(I think Bee should be high up but I'm not sure)
Intelligence
I'd consider people like Shikaku, Shikamaru, Itachi, Hiruzen and Orochimaru of equal intelligence. Their all smart in their own ways. Shikaku,Shikamaru and Itachi are very clever and quick thinkers, who can come up with strategies even in stressful situations. Itachi has also shown great forward planning, as has Orochimaru. Orochimaru is also a scientific genius. Since they've been around for such a long time, both Hiruzen and Orochimaru have vast knowledge in a variety of areas.