The rules have refocused the game in 3e, and the mode of recommended play refocused play for 2e (and then reverted pretty much in 3e).
In 1e, much more time is generally spent screwing around with things to see what they do, and also mapping. The relative sparsity of detail in the combat system allowed time for these activities. Players generally had to specify what they were doing, and die rolls for the results of these actions weren't very frequent.
By contrast, 3e has a more in-depth combat system, and die rolls are used to manage lots of things where 1e would have required exact player instructions but then no die roll (or, possibly, still with a die roll, but usually a saving throw).
Even though the rules are very similar, the focus of the 3e game onto die rolls and the attendant skill system, specific combat actions rather than one-off resolutions of "I try this," and the simple effect of "winging it" under the DM's judgment when rules didn't cover things makes 1e and 3e very different games.
As to 2e, the rules were basically the same as 1e, but there was a lot of focus at that time on how the players were part of a story and shouldn't be killed unless absolutely necessary, including fudging die rolls. 3e returned to the 1e focus of "it's a game of survival" not "it's a story of destined glory." So in that respect, 1e and 3e are very close.