<p>I want to use a template engine in a struts application and would like to know if using TILES can be recommended instead of FREEMARKER or VELOCITY.</p>

I've used tiles before on a project. It was good for templating, however it can't really be compared to velocity or freemarker: with Tiles you use normal JSPs and are limited to the JSP tags youv'e got.
Velocity (and probably Freemarker although I haven't used it before) provide their own tags or expression language, so you can do thinks like:
```
Hello ${name}
```
Which you can't do in plain JSPs. [updated due to comment: in JSP 2.0, EL is included so you can do things like that. However, I think Velocity or Freemarker are more powerful in terms of what you can do with it.]
If you've got a layout with lots of different components (i.e. header, sidebar, etc) and you want to define various different templates, tiles isn't a bad choice. (Although be warned - it can be quite a lot of XML!)
But if you need something more "advanced" than plain JSPs Velocity or Freemarker might be the way to go.