[Debezo]

I think,
'Itsumo arigatou' is appropriate for friend, instead of 'i like you'.
いつもありがとう Itsumo arigatou. - thanks, you always help me.
'sugoi tomodachi' sounds like 'an able friend or famous friend'. yoi or subarashii are better. 'sugoku(sugoi) yasashii' is ok.
いつもありがとう。あなたは親切な素晴らしい友達です 。
Itsumo arigatou. Anata ha shinsetsuna subarashii tomodachi desu.
or
shinsetuna / yasashii
subarashii / yoi
tomodachi / yuujin / shin'yuu / hito
etc...