One of the trademark gimmicks of the cartoon series based around the Pokemon brand is that the actual Pokemon say their names when talking, interacting with other humans, performing their moves, or when called out of their Pokeball. Well, there's a reason why they don't say their names in the games.
Very interesting insight.
In the anime the Pokemon simply say their names, and the intonation and inflection of how their name is said determines their mood and what they convey. In the games it's a bit different because their responses have to be contextual related to gameplay, so it's approached more-so with their "cry" being reflected upon the state of the interaction within the game itself.
However, the bigger revelation as to why the Pokemon didn't say their names in the older games like Pokemon Red and Blue or _Pokemon Green _and Yellow is something that could easily be overlooked, but was very important to the era: the hardware.
As Junichi Masuda points out, the Gameboy and Gameboy Advanced were extremely limited in how they could depict the Pokemon. For the longest time the Pokemon game series were limited to utilizing static picture sprites due to the memory limitations of the cartridge. More animated images began making their way into the games, but the limited processing power meant that they still had to rely on sprites.
These days the Nintendo 3DS is capable of fully rendered vector three-dimensional graphics, and that has allowed Game Freak to evolve the Pokemon to not only make noises but also display them in fully rendered 3D.
I suppose a better question for Junichi Masuda would have been if the hardware was capable back in the mid 1990s, would they have utilized the Pokemon saying their names in the game? It's definitely something to ponder on.