How to have post count after each listed category

For showing category count on your loop –

foreach($categories as $category) { 
    echo '<li><a href="' . get_category_link( $category->term_id ) . '" title="' . sprintf( __( "View all posts in: %s" ), $category->name ) . '" ' . '>' . $category->name.'</a>&#32;&rsaquo; ('. $category->count .')</li>';
    }

And for showing count with wp_get_archives function, use show_post_count in argument –

wp_get_archives( array( 'show_post_count' => true ));