Another one I haven't played for years and years and just revisited: Fava Beans is a solid E1 replacement and a good one if you want a chilled out, mostly really easy WAD. The level design is a cut above considering the historical context of this set, and it nails the E1 feel. Heavier monsters are introduced much earlier, but the difficulty rarely gets above casual.
E1M8 is anticlimactic and feels like a letdown after the consistency of the preceding maps, but aside from that I recommend it for an easygoing old school Doom fix. That said, it could have been harder in places. There have been better E1 replacements since, but Fava Beans is still worth a look.
Best: E1M4, E1M5, E1M7
Conceptually a pretty cool map, have a nice retextures of wall using the ice floor, giving more context to the main theme of icy cavern present here, the layout is good, some room design are pretty good for the age it was done (especially the starting area) but it's unfortunately ruined by two things: excessive slippery floors and a no exit lava pit, as well as the random nature of switches placement that activates something... somewhere. Where is not given to you to known, the same things happens for a secret (mandatory) corridors areas that connect the said grave. But despite this, is not that bad, actually!