Mikazuki is definitely my favourite of these.
But Sakuranbo, First Love and SEASONS aren't far behind at all. I love all three of those dearly.
After that, I guess, Yume no Uta, and then VALENTI and Everything are a little under that.
And all the rest.....kinda suck. >_> (Seriously, GLAMOROUS SKY is Mika's most overrated song--it pisses me off, lol.
)