Houdini was a great starting place for me, it has a good mix of what the Melvins do. The first side of the album is very approachable and chocked full of singles, primes you for the stranger songs and albums that follow. From there I'd go to Stoner Witch and then backwards to their self-titled '92 album.

I'm diving into Van Morrison's mountain of alleged masterpieces for the first time today. I've got Astral Weeks, Moondance, His Band & the Street Choir, Tupelo Honey, and Saint Dominic's Preview ready to go. It's a beautiful sunny day out, first in a long time, so I'm hoping to prime myself with his more upbeat, freewheelin', and rock oriented albums before diving into Astral Weeks which is apparently widely regarded as one of the most influential albums in the history of pop music, but I've heard it's quite an emotional head trip, I want to save it for the right morning.

So my blueprint for taking on Van Morrison in the most approachable and optimistic way possible:

1st, Moondance
2nd, His Band & the Street Choir
3rd, Tupelo Honey
4th, Saint Dominic's Preview
5th, Astral Weeks

Somebody that knows Van's catalog please correct my order if it seems off, or add any of his more upbeat work that I may have missed.

Houdini and Stoner Witch for a good taste of what you're getting into

Bullhead or Gluey Porch Treatments for maximum sludge

A Senile Animal for maximum psych

Electroretard/Prick/Honky for maximum experimental-ness

I shall remember this. Thank you very much, sir.

Melvins are my #2 all-time group so I'm always happy to be of assistance.

Who's your number one?

At the Drive-In

:beer:

:cool:

So I wrote out this whole thing, but I didn't notice how old some of the quoted posts are. I'm going to post this anyway, but feel free to ignore it.
This is a super incomplete list. Pretty much every artist on here has much more worth listening to and I'm missing a lot of essential artists. In rough order.

Sam Cooke: Live at the Harlem Square Club
Otis Redding: Otis Blue
Marvin Gaye: What's Going On
Gil Scott-Heron: Pieces of a Man
Curtis Mayfield: Curtis
Aretha Franklin: Lady Soul
James Carr: You Got My Mind Messed Up
Syl Johnson: Is It Because I'm Black
Millie Jackson: Caught Up
Al Green: Let's Stay Together
William Bell: The Soul of a Bell
Super Furry Animals: This is a tough one because, as you say, they're very consistent. I think I could probably say any of their first six, but I'd start with the debut, Fuzzy Logic, and Rings Around the World. Maybe Radiator.

TVOTR: I used to be pretty into them. I would go with the Young Liars EP and Dear Science (my favorite, and I think the one you'd like the most), but I think Return to Cookie Mountain is their most popular.
Make sure to listen to Veedon Fleece. Quieter than most of the stuff on your list but IMO his best album - it's maybe less peppy than most of what you're already listening to, but I would say a lot of it is pretty happy. If you like Astral Weeks you should like it, and even if you don't like Astral Weeks - I think it's fine but not great - you might like it anyway.