I think its kind of unfair to compare some of these substances...
All are great, well nearly all.
I would have to state that I have not used ketamine or pcp, the second one especialy is on my list of no-nos
I am not realy into dileriants either, you know, things like datura etc... you can have those experiences with a good fewer.
You have to love acid for how it can warp/reshape reality into something completely diffirent. Same of the most beautifull hallucinations based on the real world, has been on acid, things like the sea inverting its colours to turn into an electric blue expanse, little round clouds makeing a spiral 10 miles wide at the top, houses drifting down the street in streams of red magma, 4m tall dogs dragging their owners along etc... lol, its priceless.
And a valuable tool in switching on I think something like 11 genes. Most involved with higher thinking, the stuff that diffirentiates you, from your cat. So appart from the trip you are also undergoing a physical change.
"LSD induces expression changes in a relatively small but important collection of genes. Many of these genes influence the way neurons change physically to alter functional abilities in the brain. At least one of the genes is involved in the process of growth and differentiation of various cell types, and has been shown to be necessary for memory consolidation. A common theme of many of the genes regulated by LSD is the process of synaptic plasticity. The genes that LSD affects may thus play an important role in learning and the storage of memories."
Man!, I should do some acid again, its been years, you gotta love how smart it can make you, assuming you launch from a good platform. But ultimately I would say that LSD is a "weak" halucigen, in terms of the imagery, its more like the stuff you see in dreams, than being a visual cortex hijack of the highest order. I am like a mad professor when I get acid in, it totaly makes me understand that stereotype... and how mad I get!!! It actualy gets embarasing when my wife starts talking about all the shit I got up to on acid....like hiding from a ufo invasion in a portapotty- while she had to guard the door.
But how could one compare that to the mental 3rd eye imagery of say DMT, when you no longer need the two eyes you normaly see with, but instead turn on the little one between your ears... nifty little chap that, can do the functions of all the other sense organs and more when activated.
DMT, well wow, still inconceivable to me that my brain can come up with what I see there. Substances, colours, smells sounds etc you can not even conceive of normaly. Its like you can stuff everything about our known universe in a dark corner in hyperspace, and you wouldn't even notice its missing, with all the shit going on. What is realy the best part of the experience is that your mind is basicaly in tact through the experience... relatively speaking.