1) HG/SS are my least favorite games in the main series. I didn't like Gen II much to begin with, but I like the remakes even less. For some reason, even though I'm not absolutely 100% in love with G/S/C, when I fire them up I can play for hours. However, I can't do the same with HG/SS. I can't quite put my finger on it, but even playing those for 20 minutes is boring. Actually, it's not just boring... it's draining. Playing those for a bit makes me not want to play a Pokémon game for the rest of the month.
2) I haven't played OR/AS yet, but I've listened to the OST. It's... okay I guess. I feel like most of the tracks are just very watered down versions of the originals. Don't get me wrong, they do sound amazing... but they don't exactly pack as much of a punch as the originals. There are some exceptions however, namely Brendan's/May's battle theme, the Golems' battle theme, Slateport City, Deoxys' battle theme, and the Safari Zone (which I actually strongly disliked back in R/S/E... this one is so, so much better). The only track that makes me wanna mute the volume is Maxie's/Archie's battle theme. I don't think they did a good job on that one.
3) I think B/W are vastly superior to any of the games that came before, and to their sequels. Can't say anything about OR/AS and X/Y as I haven't played those so that's why I'm not all-out declaring "B/W ARE THE BEST GAMES EVAH".
I loved how they only included Gen V Pokémon, and I feel that's what they should have done in any generation. It's kinda like learning a new language. When you find yourself in a situation where you have to speak another language you haven't exactly mastered and don't have the option to fall back on your native language to communicate, you have your back against the wall. You have to speak this new language. That's what happens when you only put the new Pokémon. There are no old, familiar faces. Fans have to learn the new Pokémon's names and typings, because they really don't want to do something as stupid as using Dig on Scraggy just 'cause they think it's an Electric-type. They have to adapt to this completely new setting.
I thought it was brilliant, though I can understand why so many people have found it frustrating.
Besides this, I loved the storyline. They managed to avoid what pretty much killed the Sinnoh games - having two climaxes. You beat the League and Team Plasma at the same time, and the plot doesn't run out. In D/P/Pt, you beat Team Galactic, and then you're left to beat the last two Gyms so that you can reach the League. Without any plot behind it.
The characters were great. I liked Cheren's development. As for Bianca, it was kinda... ehh. I felt honestly bad about having to break her dreams myself since the game doesn't give you any other options, and I felt so bad when N said she learned the sad truth that not everyone can be strong. But after that, she just gets dropped and acts as a random bodyguard to people. I didn't like that. As for N, the only thing I will say is that I lost many man-points crying over his backstory. I'm ashamed of it, yes.
The music was awesome. Some of my favorite tracks are The Dreamyard, Undella Town (Autumn/Spring/Winter), N's Room, and holy noodles Unwavering Emotions was amazing. The last one too was one of the causes for my huge loss of masculinity points. Pokémon is serious biz.
Anyway, now that I'm done fanboying over the various aspects of the game, I can say that personally I felt this was the absolute peak of Pokémon games. Every little detail was on point. It was a very polished game.
When the dudes over at Game Freak get something wrong, they get it wrong. But when they get it right, they absolutely knock it out of the park.
4) Mightyena is the man. Unless you wanna use it in competitive battling... in which case, Mightyena isn't really the man. But seriously, I think it's a pretty good Pokémon to have on hand in the main storyline.
5) I hate, hate, hate graveyards. Pokémon Tower, Mt. Pyre, Lost Tower, Celestial Tower. Why does everyone put dead Pokémon in towers anyway? Do they cremate every single Pokémon? Because burying them wouldn't really be practical... or even possible, for that matter. How does one even bury a Metagross inside a tower? Man. I know the developers need a place to showcase and catch Ghost-type Pokémon, but why not try something different like an abandoned town or an abandoned mine? Anything but a graveyard. Please.
6) Not sure how unpopular this is, but I'm gonna go ahead and include it. I had never really thought about this before, but after rereading the G/S/C chapter of the manga, I think it'd be interesting to have the option of not beating the Gym Leaders and being able to wander around the region without being necessarily headed to the Pokémon League, just like Gold. I know it strays a lot from the usual Pokémon formula but I feel it'd give many options for new and different storylines.
Sorry for the huge rant, or if I sounded like I was trying to impose my views in any way. Sometimes I can get a little carried away, lol.