It looks like you’re trying to run PHP in a javascript or an HTML file. That won’t work unless you explicitly tell apache to execute .js / .html files as PHP (but you really shouldn’t).
In a kirby template:
<img <?= attr([
'src' => $image->url(),
'alt' => '',
'class' => 'shout-on-hover'
'data-title' => $image->title()
]) ?> />
In your javascript file:
$('img.shout-on-hover').hover(function() {
alert($(this).data('title'))
})