It's a fair comparison in many ways, because 5th Age involved cataclysmic changes and also included an "edition shift" in the sense that a whole new game system was introduced into the setting. And considering how vastly different 4E is from 3E, you could call it a new game, not just a new edition.
I have always been a DL fan, and yet I really liked 5th Age. I didn't mind so much about Father Chaos and the Dragon Overlords, although I must admit that all those changes made the setting actually harder for me to run. What I loved most were the innovative SAGA rules, because they truly emphasized and encouraged storytelling and we had really good times with them. Sadly, the rules were also a bit "rough" on the edges are easily exploited in certain ways. Yet it should be noted that many concepts first featured in SAGA have now appeared in various Indie RPGs, so I guess that the "legacy" of the SAGA system still lives on. I don't think that 5th Age did too well, commercially, because as we've seen, DL has returned to its "roots" in 3E.
What I've seen of 4E FR so far has been... well, quite uninspiring and lazily thought out. A lot of stuff seems to contradict previously published Realmslore, which is an indication that either the developers didn't come up with any logical reasons for a change or did not do their homework. I mean, 'Dragons of Faerun' introduced the 3E Dragonborn into the Realms, and instead of using the Spellplague to "warp" them, they are just quietly retconned away, just because the developers apparently had *forgotten* about them?!? And instead we get this Tymanther -- the whole kingdom and all -- teleporting into the Realms? And talking of Abeir... it's a nice idea on principle but Bruce Cordell's novel 'Stardeep' and the preview articles contradict the existing lore so badly that it's going to take a *massive* historical retcon to explain that stuff. And then there is the line of thought that most (if not all) "weird" stuff may be explained through the Spellplague, such as how the Planes have been "reshuffled". And yet, all "cool" things (like Netheril and Myth Drannor and the Sword Coast) were completely *protected* from the ravages of the Spellplague, because of ancient Mythals and Mythal-like magics. I mean, a magical force capable of shaking the whole *Cosmology* and tossing *Deities* around couldn't touch High or Epic Magic at all?
![Confused :confused: :confused:](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
. Wow, talk about consistency or logic there.
All in all it seems to me that 4E FR tries to combine the "best" parts of Eberron (e.g. 'Spellscars', anyone?) and the 'Points of Light' concept and remaining fiercely loyal to the Core Rules (the number of Deities, for example). This "shoehorning" is a completely new direction in design, because in the past the rules have been implemented and augmented to tailor-fit FR -- not the other way around. In any case, I've always thought that D&D is not the best system for FR, at least if we're talking about Ed Greenwood's vision and also how Ed likes to run his games. Both GURPS or something similar to DL SAGA would work far better consider the "flavour" of the setting.
As I said in the beginning, I think 5th Age DL and 4E FR are a good comparison, but although I was able to enjoy running 5th Age despite the vast changes in the setting, I doubt I'll be able to do the same with FR.