One should not confuse an edition with that edition's corebook.
The 2nd edition corebook is very spare. It has only two pages on Hermetic society - including Covenants, Tribunals, the Hermetic Code (the Oath is not even there; and Wizard Twilight is not part of the book), plus a single page for Covenant creation rules that are not really enough. It has less than one page on "mundane" Mythic Europe, and three more on supernatural Realms (no Regiones!). A lot of that stuff gets introduced/expanded only in the 2nd edition supplements, such as Covenants and The Order of Hermes.
On the other hand, the 3rd edition corebook has almost 30 pages on Mythic Europe (concise, but very evocative, including a wonderful colour map); it has 8 pages on Tribunals, Houses, and the Hermetic code (again, in my view, exactly what's needed); it has a compact (13+ pages) but fully functional covenant creation system with a lot of character. This setting material, and the truly excellent art also create a very evocative and grim mood for 3rd edition I really, really like. Finally, while the rules are mostly compatible with those of 2nd edition, they are tweaked to be just better (according to my personal taste) in a whole number of minor ways. So, I find playing with the 3rd edition corebook certainly superior to playing with the 2nd edition corebook alone; though the 3rd edition supplements are, in my opinion, not nearly as good - in fact, I'd say that 3rd edition as a whole is definitely worse than the corebook on its own.
Now, why do I find 3rd edition's corebook a serious contender against the full 5th edition line? First of all, you get it all in a single book ... and you don't risk having a perfectly legitimate concept from the corebook invalidated by subsequent material! Second, the difficulty of stuff (from ability rolls to hermetic effects) is left much more to SG eyeballing, with plenty of examples to guide one, and rules to reduce the excessive impact of the d10 roll or of good characteristics where they ought to be overshadowed by experience; while this means you can't really make Hermetic puzzles and it can create more disagreements at the gaming table, it's less "gameable" and ends up more satisfactory story-wise, in my experience. Third, Hermetic Magic is truly universal: within the Limits of Magic, you can attempt anything, without the need to go for lengthy Original Research in order to get a new Range. Fourth, botches at dramatic moments are significantly less likely, which I find both more realistic and more satisfactory story-wise. Fifth, studying Arts is simpler and better, in my view: Arts are de facto capped around 30 or so, with books being the safer way to study early on, and vis being virtually the only option to reach scores beyond 20 (I also like the fact that this makes generalists better, and makes starting magi comparatively stronger - they start with higher Arts too!). Sixth, while truly devastating magic botches can still send a magus into Twilight - and get him into final Twilight much quicker than in 5th edition - Warping is not this constant radiactivity-like force that contaminates and slowly poisons everything one uses magic on; in my experience magi use magic much more freely, which is much more fun. Seventh, the 3rd edition corebook has a bold, grim mood (strengthened by the rules for Passions, and highlighted by art I like better) and a tighter focus that somehow get lost in all of 5th's edition expansiveness.
Note than I am not saying 3rd edition's corebook is better than the 5th edition's whole line. Most likely it is not - 5th edition has too many advantages to list here. I am just saying that playing with the 3rd edition corebook alone can be a lot of fun because of a number of issues that a lot of people overlook and that I myself overlooked for many years. So I am very partial to playing with it.