I miss 1E more than 2E - though I loved both.
I loved the flowery Gygax prose, the ridiculous amount of fluff, the cheesy artwork. I had the to hit tables(later THACO) committed to memory - THACO was a piece of cake! As others have said, I also liked the clearly defined classes, with separate and distinct skills. I liked racial limitations, both in terms of stats and classes. I preferred 1E/2E multiclassing rules. The vast array of interesting magical items, the huge variety of spells and effects. Specialist wizards (and cleric domains) were a great progression. Screw political correctness, it was realistic that female characters would have a lower maximum strength than male characters. I miss the wonky stat bonuses, the vast array of polearms which nobody used, but which fed my imagination as I had no idea what most of them actually looked like(until UA)!
But most of all, I miss the old modules. They were a real boon to a teenage DM who lacked the patience and organisational skills to homebrew consistently well. They were affordable, usually interesting, and much more user-friendly than the big hardbacks they put out nowadays. Yes, the standard dropped generally after 83/84, but they was enough goodness released between 75 and 83 to keep our campaigns going for many years.
5E is brilliant, it's so easy to work with, and it has been great for a group of newcomers to the hobby who I DM for on a weekly basis. I run a heavily improvised campaign, loosely based on old plot lines I take from some of the old modules, and the simple robustness of the mechanics really install me with confidence as a DM, because I can decide so much on the fly without fear of breaking something.
But the session which proved most memorable for that new group, most of whom have been gaming for less than a year, was a one-shot 1E Tomb of Horrors. It brought them out of their shells, and taught them to look beyond the visible skills on their character sheets. That was the real beauty of 1E and 2E.