ReReplacer is an extension (for Joomla) that can handle regular expressions. But Regular expressions is something globally used. So it is somewhat outside support for ReReplacer to figure out what regeular expression to use.
www.google.com/search?hl=en&q=regula...ion+remove+html+tags
It is quite complex/difficult to replace "all except these tags".
So it is easier to do this in a tree step replacement:
1) replace the tags you wanrt to keep with something like {tagname} (so <table> -> {table}, <img ...> -> {img ...})
2) remove all remaining html tags
3) replace the {tagname} syntax back to <tagname>