It turns out these are fantastic.
The Ultimates is definitely a huge source of inspiration for the Marvel Cinematic Universe version of The Avengers. The Ultimates is the start of it's own separate universe from the main Marvel comics so they're not burdened with all the history of all the characters. It gets to assemble it's own Avengers for the very first time and it does a great job.
The pacing of the story is fast and I love that about it. Every issue moves multiple storylines forward which is something very few comics can say.
I don't really want to spoil anything about the plot because it's so good.
My main takeaway is that this is going to go into my back pocket as a recommendation for people who ask me what comics they should check out. I think most people will like The Ultimates and The Ultimates 2.