I love having a Turbo Express.  Sure any game with text is pretty much out, but there are still a lot of very playable games.  For instance, I just completed Ninja Spirit on my Express a couple of days ago.  And the Alien's Cursh/Devil's Crush games are perfect for the Express.  The Bomberman games are great as well.
Years ago I also played through Final Lap Twin on the Express, but that was a lesson in frustration as some of the codes I wrote down didn't work so I'd have to go back to an earlier code.  But I made it! (it was a long trip)
Definitely.  As per a thread on here some months ago, I decided to pick what games to take out more carefully.  Air Zonk is amazing, but again, much easier at home.
good portable games include:
PC Kid series
Bomberman (could swear they were developed with the GT in mind)
soldier series
Puznic
Alien Crush/Devil Crash
Hmmm, can't remember the rest, but think big sprites, clear colours, and in shooters, large bullets.