TheWertle has retrieved the Boss HP information from the Kingdom Hearts II: Final Mix+ Ultimania Book for Kingdom Hearts II and Kingdom Hearts II: Final Mix. I presume these are the values on the Standard difficulty:

Kingdom Hearts II

Twilight Thorn - 300
Axel 1st time - 105
Axel 2nd time - 345
Vivi Illusion - 1
Shadow Roxas - 105

Shan-Yu - 442
Hayabusa - 102

Beast - 156
Thresholder - 137
Possessor - 98
Shadow Stalker - 176
Shadow Thorn - 390

Hades
1st time - 660
2nd time - 660
3rd time - 1230
4th time - 1230
Goddess of Fate Cup - 1575
Paradox Hades Cup 1st time - 2715
Paradox Hades Cup 2nd time - 2715

Cerberus
1st time - 440
Cerberus Cup - 960
Paradox Cerberus Cup - 1995
Paradox Hades Cup - 2715

Demyx 1st time - Not Applicable
Water Bodies - 3 each
Hydra - 462

Pete
1st time - 264
2nd time - 264
Timeless River Past Pete - 123
3rd time - 123
4th time - 784
Paradox Hades Cup - 2896

Barbossa - 612
Illuminator - 26

Volcano Lord & Blizzard Lord
Volcano Lord - 351
If Port Royal Episode 2 has been cleared first - 527
Paradox Hades Cup - 2172
Blizzard Lord - 351
If Port Royal Episode 2 has been cleared first - 527
Paradox Hades Cup - 2172

Prison Keeper - 1140
If Port Royal Episode 2 has been cleared first - 1640
Oogie Boogie - 371
If Port Royal Episode 2 has been cleared first - 533

Hyenas 1st time - 305
If Port Royal Episode 2 has been cleared first - 430
Hyenas 2nd time - 445

Scar - 915
If Port Royal Episode 2 has been cleared first - 1290

Hostile Program - 640

Demyx 2nd time - 1005
Water Bodies - 5 each

Mysterious Man - 760
Storm Rider - 1216

Xaldin - 1155

Grim Reaper 1st time - 790
Grim Reaper 2nd time - 790

Jafar - 840

Lock, Shock and Barrel - 172 each
Test Subject (Experiment) - 1290

Ground Shaker - 1424

Sark 1st time - 460
MCP - 920
Sark (with MCP)- 230

Leon
Pain and Panic Cup - 357
Paradox Pain and Panic Cup - 819
Paradox Hades Cup 1st time - 1267
Paradox Hades Cup 2nd time - 634

Yuffie
Pain and Panic Cup - 255
Paradox Pain and Panic Cup - 585
Paradox Hades Cup 1st time - 905
Paradox Hades Cup 2nd time - 453

Tifa
Paradox Hades Cup 1st time - 1086
Paradox Hades Cup 2nd time - 1086
Paradox Hades Cup 3rd time - 543

Cloud
Paradox Hades Cup 1st time - 1448
Paradox Hades Cup 2nd time - 1448
Paradox Hades Cup 3rd time - 724

Hercules
Titan Cup - 1290
Paradox Titan Cup - 2250

Sephiroth - 3000

Xigbar - 1300
Luxord - Time Gauge replace HP
Card - 50
Saïx - 1500

Xemnas
1st time - 1500
Armoured 1st time - 1000
Armoured 2nd time - 1000
Dragon Left Part - 1200
Dragon Right Part - 1500
Floating Mine B - 100 (80 exp)
Spider B - 100 (80 exp)
Missile B - 100 (80 exp)
Xemnas 2nd time - 1500

Kingdom Hearts II: Final Mix

Roxas (Main Story) - 1300

Absent Silhouettes

Zexion - 708
Larxene - 1065
Vexen - 1500
Shield - 100
Clone Level 1 - 100
Clone Level 2 - 160
Clone Level 3 - 250
Clone Level 4 - 350
Clone Level 5 - 450
Lexaeus - 1578
Marluxia - 2817

Data Battles

Xemnas 1st time - 3400
Xemnas 2nd time - 3400
Xigbar - 2896
Xaldin - 3400
Vexen - 2715
Shield - 181
Clone Level 1 - 181
Clone Level 2 - 290
Clone Level 3 - 453
Clone Level 4 - 634
Clone Level 5 - 815
Lexaeus - 3400
Zexion - 2172
Saïx - 3400
Axel - 3400
Demyx - 2715
Luxord - Time Gauge replaces HP
Card - 91
Marluxia - 3400
Larxene - 2715
Roxas - 3168

Terra (Enigmatic Soldier/Secret Boss) - 3400