Monkey likes to eat peach best!

我认为没有什么不对.但感觉有点别扭,
best 当adv (superlative of well的最高级) (often in compounds 常用以构成复合词)有两个意思
(1) in the most excellent manner 最好地:the best-dressed politician 穿得最讲究的政治家 * the best kept garden in the street 这条街上收拾得最漂亮的花园 * He works best in the mornings.他早晨工作效率最高.* These insects are best seen through a microscope.这些昆虫透过显微镜看得最清楚.* She's the person best able to cope.她是个最能妥善处理问题的人.* Do as you think best,ie as you think should be done.你认为怎麽好,就怎麽办吧.* You know best,ie You know better than anyone else what should be done,what is correct,etc.你最清楚不过了.
(2) to the greatest degree; most 最大程度地; 最:the best-known/ best-loved politician 最着名的[最受人爱戴的]政治家 * I enjoyed his first novel best (of all).我最喜欢他的第一部小说.

like...best没有问题，意思是 最喜欢
主要错误在名词上，单数可数名词不要单独使用：要加上冠词；否则应用复数。
改为Monkeys like to eat peaches best！

如果best放在句尾,则是用来修饰like,但best是good的最高级,不能修饰动词,把best换成verymuch