「好きな人は結構好きだと思います」は英語で「People who like it are really into it.」と言います。「People who like it really like it.」も言えますが、「like」が二回言っていますので、あまり自然だと感じないと思うので「really into it」（ハマる）を使えばいいと思います。「結構好き」のニュアンスも入っています。
最近の若者はまだアイドルが好きですか？
好きな人は結構好きだと思います。
Do young people these days still like idols?
People who like them are really into them.
I think that the people who like it really like it a lot
people who like (something)
（そのものが）好きな人
to really like (something) a lot
が結構好き
I think that the people who like it really like it a lot
好きな人は結構好きだと思います
話す時にreallyを強調しますね。I think that the people who like it REALLY like itやI think that the people who like it really really like itなど
ご参考になれば幸いです。
People who like it probably really like it.
It’s the kind of thing that, if you’re into it, you’re really into it.
It’s not for everyone, but the people who like it tend to love it.
「万人受けではない」= “not for everyone”
カナダ 
アメリカ合衆国 
