Talking about the games in general, not just the Pokémon. (Some people say newer generations are crap because new Pokémon look like crap. That's prejudice. =S)
Anyway, what generation do you think it's the best? R/B/Y (I), G/S/C (II), R/S/E+FR/LG+C/XD (III), or D/P/P (IV)?
The third one was a good one. Of course, you needed like three consoles, seven games, and two types of cables to catch them all, XD but I like how it got that expanded.
Still, in terms of gameplay, you don't see many upgrades in Pokémon, but I like the fact that in Generation II you get to return to Kanto.
In general, though, I like the IV Generation. The story may be repetitive, but I find the competitive gameplay much better, with the physical/special split thing, and many new good Pokémon (Togekiss 8D).
So, yeah, in terms of what you want, which is your favorite generation?
Second Generation.
1. Steel and Dark types
2. Awesome new pokemon( Espeon, Umbreon, Scizor, Tyranitar, Lugia)
3. Night and day
4. Kanto
5. Mt. Silver (vs. Red fight=awesome)
6. Both legendaries
7. trading with Red and Blue
and more.
8. All the old pokemon.
Generation II is the best one for me but really all of them were great. They all stand out in their own way. For example:
Generation I- Best Pokemon
Generation II-Best Overall
Generation III-Best New Features
Generation IV-Best Music
Generation II. Those games were a perfect mix of everything.
The Pokémon (bear with me I swear it's not all I have to talk about) were fresh and exciting, but there weren't way too many. Plus, ALL the old Pokémon were accessible, either by going back to Kanto, like in the previous games or by trading with your old games. It wasn't an overwhelming task to complete your pokédex, not that I did anyway, but still. They hadn't run out of ideas for Pokémon yet (freaking Minun/Plusle and Pachirisu, anyone?) and I enjoyed seeing all the new Pokémon, plus some pre-evolutions and evolutions of old ones!
Did I mention the game let you go back to Kanto? If I did, I haven't mentioned it enough. The game let you go back to freaking Kanto. You go through everything, beat the gym leaders, beat the Elite 4, become the Champion and then what? No, not some crappy islands that are obviously added on to beef up the game a little so people don't feel gypped. They actually let you go back to Kanto and do everything all over again. Except it was a much faster process, which is more realistic. 'Cause honestly, you're the champion of Johto. You aren't gonna have a ton of problems in Kanto no matter how you spin it. There were actually lots of benefits of doing it, too. A higher level team, more Pokémon to catch, and more events unlocked.
Speaking of events... legendaries weren't so damn obnoxious! Am I the only one who hates having 30 something legendaries to catch, with like 15 more every generation? It's ridiculous these days. Not to mention they FORCE the legendaries on you. Sure, Gold and Silver might have started this with making you go get Lugia or Ho-oh or whatever you were supposed to do, but it didn't go "HOLD EVERYTHING THE WORLD IS IN DANGER AND ONLY YOU CAN SAVE IT GO GO GO GO". >:| I mean, it was annoying in Ruby/Sapphire and then Diamond/Pearl just took the cake. "OH GOD HERE'S PALKIA/DIALGA YOU HAVE TO DO SOMETHING SAVE US. OH DID WE MENTION THERE ARE PIXIES? GO RESCUE THEM. NOW TRY TO CATCH THEM, OKAY? WHAT? YOU WANT TO GET SOME GYM BADGES? NO SCREW YOU. HERE'S A LIST OF LEGENDARIES." In GSC, I think we got a grand total of 5 legendaries: the typical trio (except now they ran, which was annoying as hell but something new, at least), and then the game-specific main legendary that they made you hunt down. You could optionally get BOTH though, so it was all good. Sure, Celebi was there too but since we didn't get it, really, I choose to ignore it.
...sorry, I just really hate legendaries these days. <_< But seriously, Gold/Silver was great in so many ways! Sure, others may have added some extra features, improved mechanics a little, but GSC was amazing. They added eggs, night and day, added happiness, hold items, sorted backpack, pokégear with phone numbers omggg (I LOVED this feature), GENDERS, and probably more. But yeah, they messed with some of this stuff in RSE and I hated it. I'm glad they brought back night and day in DP and made time matter again but it still isn't totally the same and some aspects of GSC were so much better. :(
And now I'm rambling so I'm going to bed.
Lightning is right. I'm sick of finding that every person I face in the competetive market has either Groudon, Kyogre. Rayquaza, Diagla, or Palkia... or all of the above. Yes, I've had to deal with people with entire teams made up of legendaries.
Well, that could easily have been a problem back with GSC. It's just that now there are so many legendaries to choose from and they're so easy to get because the PLOT shoves them at you. It's not like you have to go out of your way to pick them up, like with some in RBY and whatnot. In GSC, you release the legendary dogs and... then what? They run around. You can spend ages chasing them if you want but otherwise the game is just as good if you ignore them. You don't get that choice anymore. Crystal wasn't one of my favourite games because it started pushing Suicune on you. But now? I'm only looking forward to Platinum because I don't want to restart Diamond and I want to play the plot again. But I don't like that they'll completely screw up the plot to ADD IN LEGENDARIES or to make Giratina more important. It's just bothersome to me. 
...so you'd rather have the plot just be "GO CATCH ALL THE POKEMON, BEAT 8 GYM LEADERS, THEN THE ELITE FOUR AND CHAMPION! KAY GO!"?
I liked the addition of the Groudon/Kyogre storylines, as well as the Dialga/Palkia ones. It makes the game story a bit deeper and more interesting than just a generic Pokemon "Gotta catch em all!" plotline.
As far as favorite gens...I'm kinda torn between II and IV. On one hand, II had the most additions, but it also seemed half-assed in Kanto and was just way too easy. On the other hand, IV made some great changes to the game mechanics and really pushed forward competitive battling, but it was lacking in Pokemon selection in the main quest (only 150? Seriously?).
I don't mind if it's added in. I just hate being forced to do it. I dunno but the plots never intrigue me. I'm never sitting there going "OH GOD WHAT HAPPENS NEXT" I'm instead thinking "Okay so... when do get to go back to the main gym battle stuff?" I dunno. It's... it's Pokémon for me. I don't expect epic plots. XD; I find them weird. Or maybe I just hate how they're implemented since they don't build up to them very well. <_<;
I want a DS remake of GSC. Just the Johto and Kanto Pokemon plus any other evolutions or pre-evolutions from the other generations.
I loved RBY, but GSC was just Pokemon perfection. After Snap, Pinball, and TGC it was nice to have a fresh and new game for a series we were all obsessed with at the time. I loved all the new stuff. The land, the characters, the features, the Pokemon. Not so true anymore now. Pokemon is just too tedious to play now. I've played same game too many times now. Playing it again with poorly designed creatures, just isn't as appealing. And RSE was such a step down from GSC in terms of...well, everything. XD
A lot of the D/P Pokemon were really good though - a lot better than the R/S ones.
I'd really love to see a DS remake of GSC myself. I'd want higher trainer levels though, as well as a more fleshed-out Kanto. Fighting Lv30-35 Pokemon (including crap like Oddish) of trainers in Kanto after beating the Elite Four is just a joke and wasn't fun at all. I want a bit more challenge if they do a remake. At least on D/P level of difficulty.