Gen 1... that would be Blaine then. The little old man who would kick the crap out of anyone who didn't have a competent water pokemon with them (which in gen 1, competent water pretty much consisted of Blastoise, Lapras, Gyarados, and tentacruel).
And Brock wasn't much of a tough fight. I just admired his style really. And how he held his own, even for being the very first gym leader (ever, if you really think about it). Take a look at the other leaders of Gen 1. Misty... Grab a pikachu from the forest and viola, Misty is down. Lt. Surge? Grab a geodude from Mt. Moon and raise it to any level you are comfortable with, Sruge can't do crap. Erika... we will skip her. Sabrina... okay, Sabrina could cause some major problems if you weren't prepared. Koga, meet Kadabra. Blaine was kind of another bad-ass, unless you started with Squirtle. And finally, you had Giovanni. The leader of team rocket. When you have your final battle with him, he has a nice range of ground pokemon, but he is oddly weak for him having such an imbalanced team. I never understood that. Giovanni had some of the strongest 1st gen pokemon, and they had some of the best moves in the game. But they must have messed up his team's AI or something, because everytime I fought him, he would get stuck in an endless loop of horn attack and Defensive Curl.
Then the E4. Why was there such a difficulty spike with them? I mean, most of the gym leaders were pushovers. Then you meet Lorelei... and your life suddenly loses all meaning. Your "badass" team of pokemon suddenly become mediocre at best, while your strongest pokemon gets kicked around like he was in a pinball machine. So you go train enough to beat Lorelei. You get past her, only to get dropkicked by Bruno. Train again, beat Bruno, get licked by Agatha's Gengars. Let's assume you beat her. Then you walk in to meet the most badass of all the trainers (of every game in my opinion... this guy truly is a legend), Lance the Dragon Master. So, you see he is the Dragon Master and you about crap yourself? You shouldn't, because his team's broken AI was never fixed and his ultimate weakness is a Zubat. Yeah, that crappy little blue bat that you left at home in your PC, hoping you would never have to look at his creepy little eyeless face. The bat that actually has a bigger mouth than Mick Jagger and Steven Tyler combined is the ultimate weakness of the original Dragon Pokemon, Dragonite.
I dont want to keep making everyone read long posts, but I have to explain how bad this actually was. Ok, so the original games' AI was simple. It had a check at the beginning of every turn, before an enemy's attack was chosen. This checked to see if that pokemon had an attack that would be super-effective against your pokemon. If it was, it would automatically use it until you were dead. So, your Zubat is out, Dragonite is about to curb stomp him into an oblivion. The AI does it's check. Zubat is a poison type and a flying type. Psychic is effective against poison, electric is effective against flying. The check comes back that Dragonite does, in fact, have one Psychic type move. So here is what you now see...
Dragonite used Agility!
Dragonite's speed rose!
Zubat used Leech Life!
Dragonite loses 10HP, Zubat gains 2HP!
And now that the game is stuck in an infinite loop due to Dragonite's AI assuming that the "super effective" attack will soon be the downfall of the nation of Zubat. You would think that after 15 turns of getting quicker, Dragonite would eventually be able to dodge the same damn leech life that has hit him 15 times. You would think that this Dragon (who's pokedex entry claims to be one of the smartest pokemon, mind you) would realize that this attack is the same one used last time, maybe it should be dodged now.
Off my rant now, lol. Anyways, BW2 adds in quite a bit. First off, it is the first real sequel in the series, so that is a plus. I know gold and silver were considered sequels to red and blue, but we all know that is bullsh*t. They took place in a country nobody apparently knew of before, and have pokemon that have apparently never been seen before (even though not even professor oak is surprised to see them, like they have always been there), and they had two kids who have nothing to do with the story of the first games. So no, I do not consider GSC to be sequels to RBY. Anyways (I guess I am in a ranting mood this morning, lol), these games also have quite a bit of new stuff to do. Like build your own Avenue, where you can let your friends and fans open shops to sell stuff to your other friends and fans, while you get access to rare items. Or even the new area type place in Driftveil, which eventually allows you to go back and battle every gym leader, elite four member, champion, and important figure from every single game. I am not kidding... in one of the final tournaments you unlock, you can fight Red, Silver, Crystal, Professor Oak, Blue, and Professor Birch... all in one single tournament! Of course, all of them are rare to find in the tournaments, but they are there, which is good enough for me. Then, you have a pretty decent story this time (good continuation). An achievement system (they call them medals though). You can make movies at the studio... There are just so many things you can do, it is crazy.