Haven't played demon souls.. But

1. Ornstein and smough

2. Father Gascoigne

3. Gwyn

4. Gerhman

5. Sif

6. Micolash

7. Velstadt

8. Blood starved beast

9. Four kings

10. Executioners chariot

Hmmm... I'll give this a shot, but not sure I can order them.

From Demon's:

Maneater, Allant, Flame Lurker

From Dark:

Kalameet, Manus, Artorias, O&S

From Dark 2:

Fume Knight

From Bloodborne:

Logarius, Gehrman

Honorable mention to Vicar and Ebrietas.

Man, this makes me realize that Dark Souls 1 has so many good, memorable bosses, and Dark Souls 2... does not.

Edit: And as the next list proves, some people really dig Dark Souls 2 :) Might be down to which one you played first.

1. Darklurker

2. Alonne

3. Ivory King

4. Abhorrent Beast

5. Loran Darkbeast

6. Gwyn

7. Gehrman

8. Vicar Amelia

9. Kalameet

10. Rom

@flumpus: I agree though, dark souls 2 bosses were primarily really really lame

Is it not just because the bosses in 2 are recycled from 1 so it doesn't hit as hard?

Nah, they're not really recycled. They tried to do similar things with some, I guess (Throne Watcher and Defender struck me as "O&S was great, let's do that again!", the Gargoyles, Sinh very much felt like a Kalameet rehash, uh, just straight up Ornstein - maybe you're right), but for the most part, they were just unimpressive and fell flat. I guess what did it for me, was there were very few that I had to bang my head against, and then felt immense satisfaction when I finally beat them. Fume Knight probably comes closest to that Demon's/Dark 1 feel for me.

1) False King Allant - this guy thoroughly establishes the principles of great souls bosses. A fairly clear tell followed up by a quick strike/combo forces the player to learn and results in extremely satisfying dodges.

2) Maneater - a bully who likes to push the player around. Unfortunately he does it on a narrow bridge. And just when you think you have him figured out his twin brother shows up. You know, the original Bell Gargoyles.

3) Maiden Astraea - her protector, Garl Vinland, is one of the most dangerous enemies in Demon's Souls. This boss commits suicide in a pit of aborted fetuses she was trying to comfort. You monster.

4) Artorias the Abysswalker - a fight in the mold of the False King, with a roided out mode that you either prevent or keep clear of.

5) Ornstein and Smough - well, it's mostly Ornstein, with Smough getting in the way a lot.

6) Storm King - you knock a demon god out of the sky with a sword that fires bursts of wind magic.

7) Gwyn - his aggressive onslaught was a great finale to Dark Souls.

8) Executioner's Chariot - while I generally hate bosses that summon regular enemies, the race to the end of the arena is exhilarating. Plus, it reminds me of Goht from Majora's Mask.

9) Sir Alonne - he only has one attack that is magical in nature, the rest is a pure sword fight between masters.

10) Darklurker - the opposite of Alonne. A user of all varieties of magic with some deceptive attacks.

I've only played Dark Souls 1 and 2 so I can't speak for all the games. I also haven't played the dlc for either of them. Personally the Four Kings fight is harder than any other fight in the games, especially when there are five freaking kings. Ornstein and Smough were also pretty tough, but I enjoyed that fight a lot more. Sif was fun, but easy to me. Pinwheel is great because he's so easy. Gaping Dragon was just amazing to look at.

@spoonman671: noo bloodborne ?

I don't think any list is complete without Artorias included in it. He is my personal favorite boss from any souls game.

1. Artorias

2. Looking Glass Knight

3. Ornstein and Smough

4. Father Gas

5. Sif

6. Darkbeast Paarl

7. Rom, the Vacuous Spider

8. Gehrman

9. Royal Rat Vanguard

10. Moonlight Butterfly

1. Maiden Astraea
2. Tower Knight
3. Fume Knight
4. Storm King
5. Ornstein and Smough
6. ruin sentinels
7. martyr logarius
8. Blood Starved Beast
9. Artorias
10. Burnt Ivory King

This is a tough subject because some bosses on the mechanics level aren't all that and a bag of chips but are great for lore or atmosphere reasons. Likewise there are many bosses that are really fun to fight but seem pretty light on the story side and can even be sort of random. So factoring both things in... this is my list. Except I am excluding everything that is not a "souls" game because that is what this thread really is "What is your 10 favorite souls bosses". If I named some bosses from earlier From games no one would know who they were anyway.

1. False King Allant was, and still is, the best boss From has ever made.
2. Saint Astrea, still the best lore/story/atmosphere boss with insanely good music for the fight as well.
3. Flamelurker
4. Sinh, the Slumbering Dragon
5. Ornstein and Smough
6. Martyr Logarious
7. Gehrman, The First Hunter
8. Old Monk (heh, if you played Demon's Souls you know why.)
9. Looking Glass Knight
10. Old King Vendrick (remember I am judging this on the lore level too)

Runners up include (in no particular order) Sir Alonne, Father Gascoigne, Daughter of the Cosmos Ebreitas, Dragon God, The Burnt Ivory King, Four Kings, Seath the Scaleless, Gravelord Nito, Adjudicator, Micolash Host of the Nightmare, and the various crap tons of Gargoyles I have killed cause I actually like those fights. Meanwhile my condolences to all the Dark Souls 1 expansion bosses I can't judge cause I had lost interest in Dark Souls 1 by the time the expansion hit and I never bothered playing it.

Sorry, but none of them really stand out to me. Shadow of Yharnam and Mergo's Wet Nurse were fun and kept me on my toes, if I'm going to call out particular bosses from that game. Unfortunately, my strategy for nearly every Bloodborne boss was dodge forward just to their right, then wail on them until they bat you away. The consequences were never severe enough to deter this.

Since this thread is still going for God knows why: Flamelurker is easily the best boss in Demon's Souls and was at the time one of the best Action RPG bosses ever for what it's worth (not to say you can't make a boss like Flamelurker that isn't up to the new standard, Abhorrent Beast is all over that shit). I don't think it even cracks into the top 30 of all the Soulsborne bosses anymore. There are 2 or 3 bosses in Lords of the Fallen that are better than Flamelurker. Storm King is the only Demon's Souls boss that ages extremely well by virtue of being really weird and kind of cool. Maiden Astraea is not a boss fight. Garl Vinland is, but he kind of does virtually nothing and is almost not a boss fight himself. False King is the second best boss in Demon's Souls and probably around 40th or so all time, a fine boss but generally unremarkable in a modern context due to fairly bad AI pathing and so forth, Gwyn could probably take on like 3 False Kings at once and win just due to having way better AI. Old Monk is a cop-out answer. Penetrator and Tower Knight also age reasonably well and Boletaria is still reasonably high up there in terms of "Worlds" in the series (probably like 4th or 5th); of course Valley of Defilement is still way, way worse than absolutely everything in the series; you would have to make a conscious effort to make something more terrible.