I thought the DSi actually has better hardware inside like more RAM and a better CPU? The GB pocket is more like the DS Lite.
Agreed. First, there was the Game Boy. Then, the Game Boy Pocket was released - smaller, lighter, better screen, but still the same basic hardware. Then, the Game Boy Color came out - Even better screen, better hardware (faster processor, etc) and games that would only play on it.
First, there was the Nintendo DS. Then, the Nintendo DS lite was released - smaller, lighter and better screens - but still the same basic hardware. Then, the Nintendo DSi was announced - Even better screens, better hardware (faster processor, etc) and games that will only play on it.
a:Spirit Trackers make it 3 in a row? Hmmmm...
Did you forget about The Minish Cap? and A Link to the Past/Four Swords.
And Phantom Hourglass - but I think the point was each major hardware iteration was bridged with a Zelda game that was basically fully playable on the old hardware but had something exclusive for those playing it on the new hardware. Of course, there was no such title for the GBA -> DS.