Well, I think almost everyone agrees about the cleric. Here's my rankings:
1)Cleric - Domains really push a cleric over the top. You're already a flexible spellcaster and second-tier fighter, and domains can add attack spells, bonus feats, unique abilities...really allowing you to make the character just the way you like it.
2)Monk - At 20th level, a fighter's attack bonus is +20/+15/+10/+5. A monk's is +15/+15/+15/+10/+5...which means only the fighter's first attack hits better than the monk. Add in enough special abilities to choke a horse, a lack of item dependence (that all other classes suffer from), and SR (!!!), and you have a really tough combo. Their only problem is their dependency on high stats...but they're much better off than a paladin.
3)Ranger - BAB of a fighter, one less HP per level, but loads more skills and special abilities. They don't have as many bonus feats...but they still get three on top of everything else. Fighters have a slight edge with heavier armor, but the Ranger is a much more flexible character, that can fill multiple roles. In particular, many adventures need a person who can track.
4)Barbarian - With the changes to DR and Rage, the Barbarian is a more durable combatant than the Fighter. The lower-magic the game is, the better off the Barbarian will be.
5)Wizard - The spell changes (especially Haste) has lowered their ranking, but they're still a solid choice...especially when you specialize. Quicken spell puts them WAY ahead of Sorcerers.
6)Rogue - Sneak attacks are horribly powerful against anything vulnerable to them, and they are the skill gods. However, against certain foes or situations they're as useless as a spellcaster fighting a high SR creature.
7)Fighter - A solid class, but one that becomes rather inflexible. The Weapon Focus and Specialization feats mean that most fighters rely on a single weapon. Take it away or Sunder it, and they lose a lot of effectiveness. They also suffer from the "diminishing returns" problem. They can meet the requirements for any feat by 12th level. This means that any feat chosen after 12th becomes something that's a secondary or tertiary choice for them. This is a class that you take for 4, 8, or at most 12 levels, then go into something else.
8)Druid - I'm probably underrating them, but they're just nowhere near the power of Clerics. 1 less spell per spell level (no domains) and no spontaneous casting of cure spells. The animal companion would place them higher on my list, but there's many times where it's just inappropriate to bring them along (good luck bringing your bear into a city adventure). The wild shape is very nice, though the lack of extrordinary special qualities is a downside (can't even see in the dark).
9)Bard - They've definately improved from 3.0. However, many spells offer morale bonuses, which don't stack with their bardic song. They can still be quite effective, especially if they focus on Enchantment spells...but I'd still rather rely on a heavy-duty caster or fighter-type in a tough fight.
10)Sorcerer - In tough combats, mages rely on their highest level spell first. Sorcerers get their highest level spell one level later than wizards, and only have one choice of what they cast at that level. They also max out at one spell/round, because of the Haste changes and no Quicken option. To top it all off, no bonus feats. People say that metamagic on the fly balances this out...but aside from Quicken, metamagic is an overpriced way to change the effect of a spell.
11)Paladin - A fighter-type with good saving throws, a few interesting special abilities, and spells. However, they're horrible under standard point buy for stats, since they need Str, Con, Wis, and Cha as high as possible (preferably 14+ in each), and an argument can be made for a 12 Dex as well (for an AC bonus in full plate). Also, they don't get ANY bonus feats...at least the ranger has two choices for a chain of three extra feats.