...if you never played either before... dont play either.
to be honest, both games arent exactly what you'd expect just from the screenshots.
monsterhunter is a really slow game, specially at the beginning. you'll have to waste countless hours collecting items, selling them, turning them into armor, getting 2 dozen armorsets, building traps and stuff like that.
fire emblem can piss you of to no end with its tendency to crit stuff in the worst possible situations.
if you have the option, check out the ds fire emblem games first to see if you have any fun with them.
monster hunter too.
one way or another, check if you like these games before you pay for them. i made the mistake of spending 30€ on monster hunter tri, it was never worth it to me. never had any fun with it.