<td>
<?php $review_link = get_post_meta( get_the_ID(), 'game_review_link', true );
if ( ! empty( $review_link ) ) : ?>
<a href="https://wordpress.stackexchange.com/questions/110077/<?php echo esc_html( $review_link ); ?>">
<div class="rating-<?php echo esc_html( $review_link ); ?>">
<?php echo esc_html( $review_link ); ?>
</div>
</a>
<?php endif; ?>
</td>
UPDATE
Thanks to Chip Bennet, this is now working code. Changed isset conditional check to ! empty.