Diamond offers everything Emerald did, but adds more.
Pokemon Diamond is for the DS and has the extra fun and interactivity of the awesome touch screen. It also obviously adds a lot more pokemon and has all or nearly all of the old pokemon. It adds 100 new pokemon to the series. Also, lots of the new pokemon are more interesting and better designed. One thing I really liked is that they didn't just add new pokemon, they gave some old pokemon an extra evolution and everybody likes evolved pokemon. It may seem annoying that while battling you have to pull out a stylus and when you finish the battle put it away because it gets uncomfortable, but it's really not a problem. In the battles, when you need to use the touchscreen, everything is in a convenient spot for your thumb to hit. In conclusion, Pokemon Diamond isn't too much better than Pokemon Emerald but is definately better. It's the best in the pokemon series unless you include Pokemon Pearl which is just as good. This game is an addictive RPG which you'll want to play until you beat it or get a game even better than it. It's a difficult game to complete since there's so much to do and so many places to go. This game takes a short amount of time to learn how to play and that time will all be worth it. So check your bank account and see if you have the $45 needed for this game (taxes not included). If you have that money and are into gaming, this is the right game.