suki ends in ki （き）, not in i （い）. Therefore it is not an i-adjective. :)
It's not because it ends in a hiragana that it becomes an i-adjective, it is because it ends in hiragana-i; い
kirei and kirai are the exceptions to the rule and therefore they are na-adjectives, even though they end in い。
suki ends in ki （き）, not in
suki ends in ki （き）, not in i （い）. Therefore it is not an i-adjective. :)
It's not because it ends in a hiragana that it becomes an i-adjective, it is because it ends in hiragana-i; い
kirei and kirai are the exceptions to the rule and therefore they are na-adjectives, even though they end in い。
I hope this helps! ^^