Highlight current tag using get_tags()

Compare $tag->term_id with the value from get_queried_object_id(). You have to cast the former to integer, because it is provided as a string for no good reason.

<ul id="blog-tags">
<?php
$tags = get_tags();
if ( $tags ) {
    foreach ( $tags as $tag ) {
        echo '<li>';

        if ( (int) $tag->term_id === get_queried_object_id() )
            echo "<b>$tag->name</b>";
        else
            printf(
                '<a href="https://wordpress.stackexchange.com/questions/109677/%1$s">%2$s</a>',
                get_tag_link( $tag->term_id ),
                $tag->name
            );

        echo '</li>';
    }
}
?>
</ul>