1. 喜欢你强调一种状态 2. 喜欢上你意思是开始变得喜欢你，强调开始的过程

first sentense mean 'Ｉｌｉｋｅ　ｙｏｕ＇．it emphasizes the speaker's feeling towards whoever he/she is talking to. the 2nd one 'I got a crush on you' or 'I fell in love with you' it emphasizes the fact that ' I fell in love' Hope this would be helpful to you!

簡單的說： 喜歡你：是自己已經知道的事實。 喜歡上你：後來發覺自己的事實。

我喜欢你：强调了一个事实，指的就是i love you. this emphasizes the fact that i' m in love with you. 我喜欢上了你：“喜欢上”是一个过程，“了”在此指的是过程的结果，即从我开始喜欢你到最后喜欢你。this emphhasizes the process and the result. i started to love you and finally i fall in love with you totally.

一个是喜欢的状态，一个是喜欢的动作（或行为啊举动啊）