How to display posts list on my plugin page?

Better would be the use of WordPress’ function get_posts():

$args = array(
    'post_type' => 'post',
    'post_status' => 'publish'
);

$posts = get_posts( $args );

echo '<ul>';

foreach ( $posts as $post ) {
    echo '<li>' . $post->post_title . '</li>';
}

echo '</ul>';

http://codex.wordpress.org/Template_Tags/get_posts