Mario and Princess

Location: Kaihin Makuhari, Japan

Mario is my favourite game since I was young.

マリオは私の若かった時から好きなゲームです。

(mario ha watashi no wakaka tta toki kara suki na ge^mu desu)

How to say favourite in Japanese
好き (suki) = like.
好きな (suki na) + noun = favourite (sth)

If you want to say very very very very like, you say
大好き (daisuki) which makes your top favourite to be,
大好きな (daisuki na) + noun