I was there for the original 151. I bought a Game Boy Color just so that I could get Pokémon. I have finished at least one game in every generation. While I have fond memories of Red/Blue/Yellow, I do not partake of the “Gen I/II was the best” nostalgia bandwagon, and can honestly say that I have always looked forward for more Pokémon, and I will continue to do so for the foreseeable future. For a different take on the amount of Pokémon, read There Are Entirely Too Many Pokémon.
While some people choose collecting, others choose Pokémon contests and some just do a bit of everything, I have always considered myself a Pokémon battler. Part of what makes Pokémon battling compelling is the vast supply of options that must be pared down to a mere six. The choice of team is almost more important that one’s actual ability to play the game. The process feels like a puzzle to solve, as I try to find Pokémon that cover each others’ weaknesses, synergize offensively, that subvert expectations, and that I simply like to use. Even with all these criteria, I still have a vast supply of choices, and I can only look forward to more.
As a credit to the game developers, the player is not overwhelmed with options when progressing through the story of the game. Each game has its own regional Pokédex that must be completed before one can open up the full-sized National Pokédex. Such regional Pokédexes are a mere fraction of the size of the National version; even in Pokémon Black Version 2 and White Version 2 it is less than half the size at around 300 Pokémon, not far from the 251 present in the nostalgia-ridden “golden age” of Generation II.
That said, the 649 Pokémon National Pokédex does sound rather high at first glance. However, only about 350 of those are final evolutions. The other 300 are typically only used by people that want to evolve them, use them for Little Cup battles, or that just think Pikachu is cuter than Raichu. Fewer still are distinct evolution families. Take away “joke” or “gimmick” Pokémon like Unown and Spinda, and the number goes down even more.
In fact, I often find that I don’t have enough options until I open up the full-sized Pokédex. I always insist on having a fire Pokémon in my team, yet found my options limited to only the Ponyta and Chimchar lines out of 17 fire Pokémon families in Diamond. Under such circumstances, I find it difficult to understand how someone can enter the Pokémon series now and feel overwhelmed.
This does not even touch on the issue of all the type combinations that have yet to be implemented. It took until Pokémon Black and White just to have a fire/dragon type. Ghost/grass, fire/poison, poison/ground, ghost/fighting, ice/bug, fire/grass, and psychic/fire are just a few of many combinations we have yet to see. Add in ability options, move lists and stat distributions, and the possibilities become limitless for all practical purposes.
Competitive battlers need new Pokémon in order to shake things up and prevent the metagame from stagnating. When a new powerhouse appears on the scene, players will scour the Pokémon list for a possible counter. The sheer power of new fighting type Pokémon in the last couple of generations has finally brought Alakazam back to his glory days in Red/Blue/Yellow.
In other words, not only does each generation bring more Pokémon, but it makes more of the old Pokémon viable. The mechanics of these games are based around battling. I am aware that many people play the games just to collect and base their team around which Pokemon they find cute rather than which are the strongest. However, cuteness and battling capability are not mutually exclusive. Vaporeon, Jirachi, Starmie, Altaria, and many more cute Pokémon are considered among the strongest in the game.
Honestly, if players did not have to play multiple games in the series to have access to every Pokémon, then I would not have any problem at all with the Pokémon games’ design philosophy as-is. Keeping the roster spread out amongst multiple games does encourage trading, which is a hallmark of the series, but many of the most desired version-exclusive Pokémon are legendaries that nobody will offer in a balanced trade. Herein lies the reason games from the previous generation still sell for almost full price, even when used. However, I consider these issues relatively minor.
Pokémon has always been a game about choices. Each Pokémon the player places on their team is a choice, as are the reasons for using them. One person may base their choices on looks, another on type, another on what will win Pokémon contests, and another on the PvP metagame. All these playstyles are supported because there are so many options. For people to consider buying a new Pokémon game, there has to be new options, and simply the only way to provide new options to every play style at once is with new Pokémon.