what did he mean side quests or main story quest?
EDIT:
i just looked it up it appears fallout 3 had 17 side quests and 11 main quests, and if you count the DLCs it all come to 45 quests.
so if you take 17 side quests x5 = 85 side quests.
32 marked quests in FO3 (without any DLC):
Spoiler
1 Agatha's Song Agatha's House Agatha
2 Baby Steps Vault 101 Dad
3 Big Trouble in Big Town Big Town Anyone in the town
4 Blood Ties Megaton Lucy West
5 Escape! Vault 101 Amata
6 Finding the Garden of Eden Vault 87 Scribe Rothchild
7 Following in His Footsteps Megaton Colin Moriarty
8 Future Imperfect Vault 101 Dad
9 Galaxy News Radio Galaxy News Radio Three Dog
10 Growing Up Fast Vault 101 Overseer
11 Head of State Temple of the Union Hannibal Hamlin
12 Name Location(s) Given by
13 Oasis Oasis Harold
14 Picking up the Trail Citadel Elder Lyons
15 Reilly's Rangers Underworld Reilly
16 Rescue from Paradise Little Lamplight MacCready
17 Scientific Pursuits Rivet City Three Dog
18 Stealing Independence Rivet City Abraham Washington
19 Strictly Business Paradise Falls Grouse
20 Take it Back! Citadel Elder Lyons
21 Tenpenny Tower Tenpenny Tower Gustavo
22 The American Dream Raven Rock President Eden
23 The Nuka-Cola Challenge Girdershade Sierra Petrovita
24 The Power of the Atom Megaton Lucas Simms
25 The Replicated Man Rivet City Dr. Zimmer
26 The Superhuman Gambit Canterbury Commons Uncle Roe
27 The Wasteland Survival Guide Megaton Moira Brown
28 The Waters of Life Jefferson Memorial Dad
29 Those! Grayditch Bryan Wilks
30 Tranquility Lane Vault 112 Brain bot in Vault 112
31 Trouble on the Homefront Vault 101 Vault 101 Distress Signal
32 You Gotta Shoot 'Em in the Head Underworld Mister Crowley
Previously, Pete said in the bulletproof pixel radio interview that Skyrim has 6 or 7 times the number of quests in FO3.
If he said today on twitter that is is about 5x, then I imagine there might be anywhere from 160 (5x) to 220 (7x).
BTW, I looked at Pete's twitter page but didn't see this comment you are referring to.