Wow that's a tough one. There's a lot of close ties; it's like splitting hairs.
There's also so much gear I haven't heard (for example, most of the 2018 KZ stuff, no TFZ products, no >$1k IEMs, no Nine Tails, no BGVP DM6 or DMG, etc.). I only rec stuff I've heard or own.
You can get a pretty good idea of the stuff I own from my profile. Most all of it is <$100, so my recommendations are based in that realm of experience. I'm sure if I was used to $2500 IEMs, everything I currently own would sound like 'junk' in comparison.
I appreciate many different tunings, but my ideal tuning leans towards:
- A mild/shallow v or u shape with slightly elevated mid-bass
- Energetic (but not piercing/sibilant/fatiguing) treble
- Good clarity
- Good extension on both ends (although some stuff has rolled-off sub bass which is acceptable even though it's not my 1st choice)
- It shouldn't be dark or veiled
- I don't like overly forward/boosted mids. I would rather have them be flat or slightly recessed
- A fun and balanced overall sound
- If something has to be forward I would prefer forward treble
You'll see my below choices reflect my preferences.
Also be aware that factors such as age and genres affect things. I don't listen to classical/orchestral for example, and I am over 40 so my tolerance for treble is higher that if I was 20.
So with that all said, I would say my favorite IEMs out of everything I've heard or owned would be ANY on this list (which is not in any particular order):
- Timmkoo C631
- Modded BlitzWolf BW-ES1
- TinAudio T2
- Pioneer SE-CH9T
- UiiSii CM5
- Magaosi K5 v2.0
- Campfire Audio Comet
- KZ ZS6
- KZ ED9
- KZ EDR1
- Magaosi BK50
- VSonic VSD5S
- BQEYZ KB1
Some of the above do some things better than another. Some are good all-rounders. Some are extreme value champions (EDR1). But if I was stranded on a desert island, I would be happy taking any of them.