Yeah, the scenes in Bag End are all really splendid---so important to get across the homey, earthy values of the Shire, before they're plunged into adventure. When he reveals his true power, yes... an important moment.I think there will be few naysayers about Ian Mckellen. What FOTR (film and book) transmits is the importance of friendship i.e. fellowship. This is well set up in the scene where Gandalf wants "just tea" (bumps his head on the chandelier - a lovely touch) while Bilbo offers him so much choice then asks if Gandalf minds if he eats something (just like a true hobbit). Then later McKellen reveals something of his true power when there is the dispute over the Ring. Mckellen manages to convey majesty and yet glories in friendship with humble hobbits.
That's always a point I enjoy, both in the book and film... that while someone like Saruman, grand as he is, might think he's above the likes of hobbits, Gandalf sees better.