As series go I'd say:
1. Devil May Cry (1, 3 and DmC)
2. God of War (1,2,3)

Awesome game too.

Haven't played too many as I generally don't enjoy the genre(I hated hyrule warriors) however I bought Bayonetta 2 over the weekend and it is simply amazing. It's by far my favorite hack n slash ever although lords of shadow was pretty cool too.

God of War. My favorite is GOW 3. Tight gameplay, nice story, giant scale. If Ascension was in the same level, it would win easily with the multiplayer, but GOW 3 is a better game.

God of War dominates my favourite hack 'n' slash list, top 10 would be:

1. God of War III
2. God of War II
3. God of War: Ghost of Sparta
4. Castlevania: Lords of Shadow
5. God of War
6. God of War: Ascension
7. God of War: Chains of Olympus
8. DmC: Devil may Cry
9. Bayonetta
10. Dante's Inferno

Bayonetta is leaps and bounds ahead of any other Hack n Slash game Ive ever played.

I mean.

Bayonetta is just fabulous.

That is an interesting game to mention, because I've had friends that completely hate it, yet there are others that fell in love with it. I haven't played it, so I can't comment further, though.

GoW is the best in every way for me.

Toukiden

Dante's Inferno was the one I enjoyed the most, but DmC was the best overall (terrific voice acting, great controls, funny moments, amazing soundtrack).

Heavenly Sword was also great, just not as great (a bit short, but had my all time favourite voice acting).. God of War is all sorts of impressive but I really, really don't like Kratos and thus find myself not enjoying the game as much as I could because of him.