Regex HTML help

Don't use a regular expression to parse HTML. Use an HTML parser. There is a good one here.

If you already have the HTML in a string:

string html = @"
<span class=""releaseYear"">1993</span>
<span class=""mpaa"">R</span>
<span class=""average-rating"">2.8</span>
<span class=""rt-fresh-small rt-fresh"" title=""Rotten Tomatoes score"">94%</span>
";

Or you can load a page from the internet directly (saves you from 5 lines of streams and requests):

HtmlWeb web = new HtmlWeb();
HtmlDocument doc = web.Load("http://www.rottentomatoes.com/m/source_code/");

Using the HTML Agility Pack:

HtmlDocument doc = new HtmlDocument();
doc.LoadHtml(html);
HtmlNodeCollection spans = doc.DocumentNode.SelectNodes("//span");

Now you can iterate over them, or simply get the text of each node:

IEnumerable<string> texts = spans.Select(option => option.InnerText).ToList();

Alternatively, you can search for the node you're after:

HtmlNode nodeReleaseYear = doc.DocumentNode
                              .SelectSingleNode("//span[@class='releaseYear']");
string year = nodeReleaseYear.InnerText;