I suppose I'm probably one of those people the OP dislike so much; my favourite gen was gen 2 (although FRLG, which I suppose are gen 3 technically, are IMHO ever so slightly better than gen 2). I've never liked gen 4 or gen 3 much, although gen 4 was an improvement over gen 3 (or at least, DPPt was better than RSE. FRLG I've already said are good games). People like the OP assume it's down to nostalgia, but that would imply we remember things being better than we actually were and would be disappointed if we tried to go back to them. That's bull. The only pokemon games I play at all any more are Crystal and Leafgreen. A quick run down of the gens, as I see them.
Gen 1: Best 'mon design by a mile, but the technical aspects of the game were severely lacking. Kanto also had some cohesion issues; it felt like more of a set of unconnected places sometimes (particularly with respects to Pewter and Viridian, although after you passed through Mt Moon it felt much more cohesive. This is more a minor gripe with the opening stages of the game).
Gen 2: Best region thus far. The only one of the regions to truly feel like a place rather than just a series of disparate locations. 'Mon design was good, although not quite on a par with gen 1 (hence why the availability of gen 1 mons was good). Only real gripe with this gen is that Johto didn't get as much of the limelight as it deserved, and was shortened somewhat to fit in a watered down Kanto, but it gets bonus points for managing to fit in some playability after the E4.
Gen 3: FRLG were brilliant. Kanto still suffered from some of the issues I mentioned in gen 1, but the technical issues from back in the day were all sorted and the Sevii Islands were a fantastic addition; the only area in any other game that feels like a real place on a par with Johto.
RSE on the other hand; well, where do I start. They took a step back in region design; although the varied environments were kinda cool, it suffered from "disjointed collection of unrelated places" syndrome much worse than Kanto did (almost as badly as FF7 did, but that's a whole nother story). Many 'mon were knockoffs of earlier 'mon (Zigzagoon line, Beautifly line, Skitty line, Aron line to an extent, Plusle and Minun, Swalot line, Seviper, Corphish line, Feebas line, Walrein line, Salamance line... I could go on), and many of the others were two-for-one deals (Volbeat/Illumise, Minun/Plusle, Lunatone/Solrock, a few others), and a very few were just plain bad (Blaziken, which looks like a three year old drew it. Seriously, they showed they could do fire on a pokemon properly with Charizard etc then give us that?). I'm not saying that earlier gens weren't guilty of one or more of these things on occasion (the Nidoran lines come to mind as a two for one deal), but not to anywhere near the same extent. The villains were utterly ridiculous after Team Rocket - a crime syndicate to a group of brightly coloured eco-nuts is a major step down. The fact that the later stages of the game were entirely water based routes was, while quite a cool concept (the whole land/sea duality thing they had going), a very badly thought out idea given how many pokemon it essentially rendered unusable for the last two gyms.
Gen 4: Sinnoh had so much potential, I'm gutted they wasted it. Almost as cohesive and realistic a place as Johto, it seemed at first like just maybe they'd got back on track. The 'mon design was a slight improvement from gen 3; whilst there were still knock-offs (Starly line to name one briefly), the main problem here was its over-reliance on new evo's for earlier mon. Gen 3 had the right idea even if they went about it extremely badly; new gen should introduce new 'mon, not minor changes to old mon. Admittedly gen 2 was an offender here too, but not to nearly the same extent. From a technical standpoint it was the best; the physical/special split was well done, although the pseudo-3D effect left lots to be desired. The main problem's then; fewer new non-legendary mon than any previous generation (even with Platinum, only 89 mon in the Sinnoh dex are new non-legendaries; fewer than gen 2, and that's counting the evo's and pre-evo's of old mon. Remove them at it ends up around 70 iirc.). Secondly, Team Galactic. I thought they'd hit an all time low with Magma and Aqua, but apparently not; the plot was ripped straight from a 15 year old RPG ("bad guy want's to become a God, and only the 10 year old kid can stop him because no-one else cares obviously!"). Seriously, it makes the plot of the original FF look good. That leads me on to the ridiculous legendaries; Groudon and Kyogre, were a little far, but not too bad. The creators of time and space? God in a pokeball? What the hell were they thinking when they decided to do that.
Tl:dr version; some people prefer the earlier gens for valid reasons, despite the technical limitations of the day. Hence why people are so hyped about HGSS.
