Depends which you think is more painful:
1. Naruto - Never knowing the love or even respect of others for the first 12 years of his life. Living in complete loneliness. As well as being discriminated against and hated for something that couldn't be changed nor something that posed a direct threat to anyone.
OR
2. Obito - Having a somewhat lonely early life without family who supposedly died but finding others to fill the void, only to lose his loved ones again spiraling back in to deep sadness.
For me the fact that Obito had family, lost them, was lonely, found others to fill the void only to have them taken away from him as well makes it hard me to choose who had the harder life between the two.