Gandalf the White could see play in legend-heavy Commander decks with white mana as a support card, but on the whole, legendary flash isn't a strong enough effect for Gandalf the White to be a viable Commander
You have to pay three up front, instead of two
Noctis, Prince of Lucis With Noctis, Prince of Lucis, your graveyard becomes a second handat least for artifacts
Scion of the Ur-Dragon One of the coolest dragon commanders around, Scion of the Ur-Dragon lets you pay a small fee to transform into any dragon in your deck
You can also lean into Izzet and take advantage of double strike + connive + combat tricks on an unblockable creature
Dance, Pathetic Marionette