I have made the switch from 4e to 2e a couple months ago, and I'm a player in a 3e game. I've thus had the experience of playing the games fairly close to each other. I think then I have a somewhat unique perspective of having the experience of each edition fresh in my mind. Here are my experiences, with my first post being about combat length.
Combat Length:
I was surprised by the fact that 3e combats are much longer than I remembered and I'm not saving any time over 4e. 3e and 4e both take 1 hour + for every mildly challenging encounter. I remember 3e combats being long, and 4e combats being worse, which I had blamed on the high defenses and hit points of 4e monsters. I think this is because once you blow your encounters and daily powers you are going to expend, you are pretty much done with the encounter and want to move on, so the "mopping up" with your at-wills is particularly dreary. 3e on the hand never gets as interesting to play as 4e, though it requires all the same minis. 3e doesn't really have teamwork or tactical positioning, so there isn't much to gameplay other than whittling down hit points or getting off a particular spell. So to sum up, 4e gets tedious after you blow your best powers, while 3e never really gets exciting to begin with.
2e on the hand has much faster combats. When I first got back into 2e as a DM, I was amazed at how quickly we would get through combats. The first time saver was that minis were much less necessary, so you don't need to dig them out and set them up for small encounters. Second, monsters generally have less hp than their 3e (and especially!) 4e counterparts, so they go down after 2-3 swings, which is generally about as long as a fight can hold your interest. 2e combat suffers at low levels when PC's don't hit very often, so it is often 3 or 4 rounds between someone striking a blow. That gets tedious fast, and combat would be even faster with a little tweaking in that regard. I like the fact that higher level PC's hit more often than lower level PC's (thanks to the AC ceiling) but it drags out too long at low levels.
2e also loses its speed when you have a large fight that includes spellcasters and armoured opponents. Last session, I played a combat that involved some human pureblood cultists, a blood elemental, 2 Yuan-ti halfbloods and a banelar naga. Between the spellcasters denying actions (suggestion, hold person polymorph etc), the poisons, the hp stealing blood elemental, and the high AC of the yuanti this fight took almost 2 hours. 4e regularly chews up combats of similar epic scale in less time, and more interestingly. However, it is much more tolerable to have a few fights that take a long time if they are epic, than to have each combat be a grindfest.
Verdict: 2e wins the combat length and enjoyment of combat aspect of the game, with 4e coming in 2nd. 3e is the least enjoyable combat experience for me.
Combat Length:
I was surprised by the fact that 3e combats are much longer than I remembered and I'm not saving any time over 4e. 3e and 4e both take 1 hour + for every mildly challenging encounter. I remember 3e combats being long, and 4e combats being worse, which I had blamed on the high defenses and hit points of 4e monsters. I think this is because once you blow your encounters and daily powers you are going to expend, you are pretty much done with the encounter and want to move on, so the "mopping up" with your at-wills is particularly dreary. 3e on the hand never gets as interesting to play as 4e, though it requires all the same minis. 3e doesn't really have teamwork or tactical positioning, so there isn't much to gameplay other than whittling down hit points or getting off a particular spell. So to sum up, 4e gets tedious after you blow your best powers, while 3e never really gets exciting to begin with.
2e on the hand has much faster combats. When I first got back into 2e as a DM, I was amazed at how quickly we would get through combats. The first time saver was that minis were much less necessary, so you don't need to dig them out and set them up for small encounters. Second, monsters generally have less hp than their 3e (and especially!) 4e counterparts, so they go down after 2-3 swings, which is generally about as long as a fight can hold your interest. 2e combat suffers at low levels when PC's don't hit very often, so it is often 3 or 4 rounds between someone striking a blow. That gets tedious fast, and combat would be even faster with a little tweaking in that regard. I like the fact that higher level PC's hit more often than lower level PC's (thanks to the AC ceiling) but it drags out too long at low levels.
2e also loses its speed when you have a large fight that includes spellcasters and armoured opponents. Last session, I played a combat that involved some human pureblood cultists, a blood elemental, 2 Yuan-ti halfbloods and a banelar naga. Between the spellcasters denying actions (suggestion, hold person polymorph etc), the poisons, the hp stealing blood elemental, and the high AC of the yuanti this fight took almost 2 hours. 4e regularly chews up combats of similar epic scale in less time, and more interestingly. However, it is much more tolerable to have a few fights that take a long time if they are epic, than to have each combat be a grindfest.
Verdict: 2e wins the combat length and enjoyment of combat aspect of the game, with 4e coming in 2nd. 3e is the least enjoyable combat experience for me.