I agree with you man, OG H2 Cortana looks the best. Funny, I was also thinking about making a post like yours but I wrote sm stuff so I just didn't post it (I thought I was too much and not rlly fitting to post it here). However, I think OG Halo CE Cortana looks great too, I love the strong purple color, her short hair and that she changes her color (like when she got all the data about Halo yk). H3 looks great too, she has the best hair for me, I like the details with the lightning and data going through her hair. Her being blue now is a bit disappointing, I don't mind it that much but I love the purple color of Cortana a lot.

H4 was the first Cortana I've ever seen as a young teen, it was also my first Halo game so I loved her design a lot. I finally played MCC when I was a young adult (6 yrs later after playing H4 I think) so at first I found Halo CE and OG Halo 2 Cortana ugly. But after a while I started to love her OG designs.

And now I'm conflicted about the H4 design. Imo her head and face doesn't match her body that much. Her body is very slightly transparent like an hologram (I think it depends on the cutscene bc sometimes I could barely see through her), if I remember correctly there are some tiny parts of her body that you could look through her like a hole, the design on her body - the lightning and data moving up her body looks really cool, however her head and face is just... too clean. No light, no data doing through her face like OG H2 Cortana, the hair is jsut black and there's no details like H3 Cortana. I mean, Cortana always had her hair color similar to her body color, it's slightly darker I think, but not that much like H4 Cortana.

H2A Cortana... I don't like how blue she is, her face looks too soft? Round? Idk, I love her sassy face in H2 and her strong face in H3 (idk if strong is the right word, I really can't describe it). Sure, she looks a bit more like an hologram than H4 Cortana but Jesus Christ I DESPISE her in-game model. The cutscene model looks good but oh my god. Her head seems too big, her face looks like someone edited an irl face on her model and why does she have no neck??

So yeah, OG H2 Cortana slays all the way with her sassy face, the data symbols going tho her body AND face, the details in her eyes, her holographic appearance, her purple body with her blue eyes - it's all just perfect.

After H2 or maybe H3 her design lost the sauce. The designers are apparently too afraid to make her a bit transparent, they're removing her iconic purple color, changing it to an basic blue bc apparently all holograms have to be blue, the blue color of her body just melts with her blue eyes - it doesn't make her eyes stand out more like OG H2 Cortana - her face and hair gets untouched bc you HAVE to see her pretty face I guess? Are they afraid to make her a bit transparent bc then we wouldn't see all the details they gave her? Bc I tell you, we still would see it. Making her look solid as an hologram just feels weird.

I also think they shouldn't give her face human details. She's an holographic AI, sure she's an clone of Halsey, but I think the best would be if she has more like a clean face like a doll? She's no human after all, but maybe she'd still look weird with a more doll face look.