I'll quote myself from the Wizards board, why not.

Quote Originally Posted by Me
I find it amusing how so many people kicked up their feet and screamed that nothing could come off the Legacy banned list, because the cards were all too powerful, and then some of those same people are saying to give Flash a chance. Let's compare the cards on the Legacy banned list that weren't banned for non-power related reasons (physical dexterity and ante cards):

* Balance- Yeah, it's Wrath + Armageddon. However, why spend two mana in a weaker color trying to get a slight mana advantage and stabilize the board, when you can spend two mana in the best color in the game, at Instant speed, and win the game right there? Clearly less powerful than Flash.
* Bazaar of Baghdad- Not even close. A draw engine that needs the entire deck built around it and inherently slows your clock by taking a land drop and not producing mana.
* Black Vise- Are you kidding? This gives them multiple turns. Flash kills them immediately and has less outs like, oh, I don't know, mulliganing.
* Channel- Channel-Fireball costs more mana than Flash-Hulk, and in worse colors with less protection and dig. I suppose you could power out a Sundering Titan or Darksteel Colossus, and scoop to Swords to Plowshares, but that's a turn 3-4 win at best.
* Demonic Tutor- 1B, try to find a win, versus 1U, win the game.
* Dream Halls- Ha! Yeah, good luck resolving that.
* Earthcraft- 1U, win the game right now, vs. 2GGG, win the game next turn unless they have Sharpshooter. Hrm....
* Entomb- Oh no, they could have a first turn Akroma. Why, that's a turn 4 kill, that is.
* Fastbond- What does an extra land drop or two matter when winning costs 1U, again?
* Frantic Search- Arguably this would break Solidarity in half, but the problem is that Solidarity is still pretty much strictly worse than Flash. Maybe if they started running Stifle and Spell Snare. This one might be almost as good as Flash.
* Goblin Recruiter- Yeah, FCG's turn 3 combo out win that costs 3GR over two turns doesn't scare me as much as Flash. Not to mention that Flash never died to Wing Shards.
* Grim Monolith- Not even close.
* Gush- Two islands to your hand? You had time to drop two Islands?
* Hermit Druid- 1U, win the game vs. 1G, pass the turn, hope my 1/1 doesn't die before he can untap, mill my library, hope the opponent doesn't have StP. Or, y'know, Fog.
* Illusionary Mask- Three mana for a 12/12 that dies to StP or Disenchant, or two mana to win right now. Difficult choice.
* Imperial Seal- I guess this makes Flash slightly more broken.
* Land Tax- Ha!
* Library of Alexandria- You'd better not still have seven cards in hand if you're planning on winning.
* Mana Drain- If Counterspell weren't obsoletely slow, this might be a good card.
* Mana Vault- With any luck, you could first turn Chalice on 2.
* Memory Jar- It'd be broken in half... if you could actually play it fast enough for your opponent playing Flash to care. Or through your opponent playing anti-Flash who just Duresses or Forces it.
* Metalworker- 3 Mana 1/2 that might do something next turn < 2 Mana Instant that wins right now.
* Mind Over Matter- Ha!
* Mind Twist- Maybe you can actually stop Flash with this... and a handful of Moxen...
* Mind's Desire- What is this "six mana" of which you speak?
* Mishra's Workshop- Maybe you can resolve a Chalice for 2 early enough to matter with this.
* Mox Emerald- What good mana acceleration when you can win for the cost of a Wild Mongrel?
* Mox Jet- What good mana acceleration when you can win for the cost of a Hymn to Tourach?
* Mox Pearl- What good mana acceleration when you can win for the cost of a Disenchant?
* Mox Ruby- What good mana acceleration when you can win for the cost of a Goblin Piledriver?
* Mox Sapphire- What good mana acceleration when you can win for the cost of an Impulse?
* Necropotence- Why do you need to pass the turn? I guess it's a good fallback against all the discard decks trying to kill Flash.
* Oath of Druids- Yeah, a turn 3 6/6 Hastey guy is really scary when it's backed up by Force of Will and Duress. Not as scary as a turn 2 win backed up by Force of Will, Daze and Pact of Negation, but I guess you can't have everything.
* Replenish- HA!
* Skullclamp- Why are you playing creatures? Why are you paying mana to do things with them?
* Sol Ring- I suppose you can power out an early Sphere of Resistance with this. That might be pretty good. If they don't have ESG....
* Strip Mine- Winning the game costs two mana in this format, and disruption had better be one mana or free. Is this going to slow them down? Why isn't this an Underground Sea so you can Duress with Daze backup?
* Time Spiral- If you shaved this price down by a third, you could just go ahead and win. Instead of putting the win in their hand.
* Time Walk- It's like a free cantrip that empties the storm count. You know what combo deck could really, really use this, and loves it's 1U spells?
* Timetwister- No, I'm trying to be serious.
* Tinker- I suppose you could get a Nullstone Gargoyle with this. That might be pretty good. If they don't draw a Lotus Petal, I mean.
* Vampiric Tutor- I suppose this would make Flash-Hulk more insane, if such was possible.
* Wheel of Fortune- If you cut off one mana and switched that ugly red mana symbol for a nice Blue one... and then maybe change that ugly Sorcery line to Instant... and that clunky card drawing thing with just winning...
* Windfall- Yeah, good thinking, they might need help drawing into the combo.
* Worldgorger Dragon- I guess 1B sorcery-speed kills that are highly vulnerable to removal from every color, instead of simply blue-black, and leave you with no permanents when you fizzle the combo are too powerful?
* Yawgmoth's Bargain- Who has six mana?

For reference, here's the entire list of banned cards that I can think of plausible arguments for, as to why they're more powerful/format warping than Flash-Hulk:

* Ancestral Recall
* Black Lotus
* Demonic Consultation
* Mana Crypt
* Tolarian Academy
* Yawgmoth's Will

Obviously, this is an overly generous list. Black Lotus, for instance, probably isn't that powerful in relation, for the same reason I listed for the Moxen. Consultation is only an enabler, and doesn't have great synergy with what would clearly be the best deck in a format where Flash and Hulk remain legal.