Smartphones usually do not outmatch the devices they are supposed to replace. Being limited to pocket size basically ensures this. In contrast, computers usually are much better at everything. With a computer, you can play mp3/tv/video; write email/docs/programs; make and receive phone calls; read Kindle books; and play anything from Solitaire to Starcraft 2. And it does this better than mp3 players, TV's, typewriters, telephones, Kindle tablets, and Playstations.
Smartphones can "do" a lot of the things other devices can, but it's usually not pleasant in comparison and for that reason I see them as backups or benchwarmers and I don't see them as a fun toy to spend lots of money on.