If you mean games like Black 2 and White 2, then you don't need to get a 3DS to play them. While having a 3DS with the games does allow you to use features such as Dream Radar, it isn't really worth it.
If you mean X and Y though, well, that's the reason I'm getting a 3DS. But getting one for X and Y alone probably isn't a good idea. However, there are plenty of good games for the 3DS, such as Shin Megami Tensei, Kid Icarus, Luigi's Mansion, Fire Emblem, and some classics such as Ocarina of Time and Star Fox. Plus some upcoming games such as Donkey Kong Country and a new Mario&Luigi game. There are also some other Pokemon games such as 3D Rumble Blast and Pokemon Mystery Dungeon.
Really, it depends on your money situation and whether you think there are enough games to make it worth buying. For the Pokemon games alone I wouldn't say it is worth buying, but you might think differently. You can get a refurbished (meaning a used 3DS but one that has had any problems it might have fixed by Nintendo, making it pretty much good as new) 3DS from Nintendo for only $120.