Basic Mechanics
1. Why is Dragon a type in this game? There is one family of Dragon Pokemon, the Dratini line, and a single move, Dragon Rage, which does fixed damage. Unless having tons of types is really important, there is no reason to have the Dragon type at all.
2. Same with Ghosts. The single Ghost line in this game is part Poison and lacks the moves to make it useful against Psychic types, thus negating the entire point of the Ghost type. That's two pointless Types from the word go. GameFreak could have instead included more Pokemon in other under-represented types, like Fire, Electric, and Fighting.
3. In Pokemon Red/Blue/Yellow, inventory space is very limited. Your Bag holds a total of 20 types of items. This encompasses every type of item though. Those 99 Revives take up the same space as an Old Rod or just one Revive.
4. Even your PC can't hold all the junk you will end up collecting unless you feel inclined to use every TM as soon as possible.
5. Also, I would like to point out that this universe has the technology to stuff an 8.8 meter long Onix into a ball that fits in a child’s hand, making all of these inventory issues nonsensical in-universe.
6. Money is surprisingly rare. You lose half your money every fight, and since there's nowhere to keep it like in Gen 2, you will be instantly poor after losing a fight. And since trainers never fight you again, there is basically a fixed amount of cash in the game until you can beat the Pokemon League. Said amount shrinks drastically if you are saving up to buy expensive items and get beaten in a fight. Meaning that you are encouraged to spend al your money as soon as possible, but are occasionally penalized for doing so.
7. The first generation of Pokemon games were remarkably glitchy. Focus Energy and Dire Hit, which were supposed to quadruple the rate of critical hits, actually cut the rate by three quarters. Extremely high or low stats could cause the game to freeze or stats to roll over back to zero during battle. Every move except Swift has an extra 0.4% chance to miss. Pokemon that went up more than one level at a time could miss out on learning moves, making training weak Pokemon a pain. It’s far from unplayable, but these are still problematic.
8. When a Pokemon is affected by Sleep, it takes an entire turn for them to wake up. During this time, they can be put to sleep again by a faster opponent. Sure, Hypnosis is inaccurate, but Sleep Powder has a 75% success rate, and even Hypnosis hits more often than not. This removes much of the risk of using Sleep-inducing moves, making it the best status ailment to use. There should not be a best status ailment.
9. A Frozen Pokemon could only be thawed if the enemy used a Fire attack or if their trainer used an item. This would be even worse than Sleep if it weren’t such a rare ailment.
10. Moves that lasted several turns, such as Wrap and Fire Spin, did not allow the target to move during their duration. This most serves to waste time and frustrate players. It’s enough to make you wonder why they aren’t single-turn multi-hit moves like Fury Attack.
Opening Act
11. What is up with the Bulbasaur family? The initial starting Pokemon aren't that bad, but Bulbasaur definitely gets the worst final form of the trio. Charmander becomes a dragon, Blastoise gets a couple of cannons, Venusaur gets a flower. And aesthetics aside, Venusaur doesn't learn as many useful moves as its counterparts. No wonder Charizard and Blastoise were the ones on the front of the game in the West.
12. As for Charizard, why is it not a Dragon? I already mentioned the lack of Dragon Pokemon in G1, and there is no shortage of Flying Pokemon. A Fire/Dragon starter would have been cool.
13. Pokemon Yellow has the worst starter in the franchise. You are given a Pikachu that can not evolve before items like the Light Ball existed. Other than dealing with Zubats on Mt. Moon and Misty, it is obsolete as soon as you get a Mankey, Nidoran, or Butterfree before the first gym. It is ineffective against 3 of the first 4 gyms and too weak afterwards. Worse, the damn thing will whine every time you put it in Bill's PC, ruining the primitive Happiness mechanic. Either you can be happy, or your Pikachu can.
14. Professor Oak does not remember his grandson’s name in the opening of the game, despite living in the same small town. This always struck me as odd, but maybe it’s because Oak is having mental problems due to his age or something? Except according to Pokemon Platinum, Oak is 47 during the events of Gen 1. So he’s just a jerk.
15. The first thing you do with your starter is cross Route 1. There, you get stuck in Viridian City until you complete a fetch quest. This is padding, and it sucks.
16. You only get the Pokedex after going across Route 1 the second time, and only get the Poke Ball tutorial after the third trek across the route. Until then, you can only fight or run from foes due to your lack of equipment and the Poke Mart not selling anything.
17. When the Poke Mart finally does open up, they don't sell Potions (except in Yellow). Why the **** would you sell Burn Heals and not Potions? Burn Heals are mostly useless until late in the game, while Potions would be the most useful at this point. You're just going to get new players to waste money on useless garbage they won't know is nearly useless until much later, when they actually can afford them.
18. Route 22 is a great place to capture party members, especially in Yellow, but putting the Rival here with a tough team early on is cruel. His team is pretty tough if one happens to wander here early on, especially if they haven't caught any Pokemon yet and are just looking around. Plus, in Red/Blue, you can not counter your rival’s Charmander if you chose a Bulbasaur.
http://cdn.wikimg.net/strategywiki/images/f/ff/Pokemon_Yellow_Rival.png
19. Route 2 is surprisingly dull. At least give us an item to find or a trainer to fight. Sure, the patch of grass contains Bugs, but considering the nearby Bug-themed forest, that's not exactly exciting.
20. About 30% of wild Pokemon in Viridian Forest are literally incapable of attacking you. This probably convinced countless children that letting their Caterpie or Weedle evolve would make them useless. That is possibly the worst lesson to for the game to teach about Evolution in this series.
21. Bug Catchers have largely disappeared over time, and this game shows why nobody cares. They trained their Metapods and Kakunas to be stronger than the wild Pokemon, but still only use Harden? The game's first dungeon should not be so tedious.
22. Red and Blue both make one of the two Bugs rare, but not impossible to find. Interesting, but I should be running into Caterpie/Weedle more than 5% of the time. Yellow solved this problem... by completely removing removing the Weedle. Yay?
23. Pewter City is a decent place, but the Science Museum is a nasty newbie trap. The fee is not too high, but considering the lack of tangible rewards and the scarcity of cash, it only serves to punish the curious player.
24. Brock's Rock-type Gym is pretty nice, giving the basic formula of being able to avoid gym trainers at the cost of XP and cash, but he obviously hired the wrong trainer. He uses a Diglett and a Sandshrew, neither of which have anything to do with the Rock-type.
25. Brock himself is a good fight, but there has to be a better TM for him to give than Bide. Even sticking to this generation’s Technical Machines, Rage would be a great fit.
Love and tolerate.
