what are some good import titles?
If you don't have any system at all yet then its not a matter of what the good imports are, its a matter of what good US games there are. Of about 700 games released in Japan, about 130 of those came out here in the US. There are very few US exclusives and only a couple of those are even playable. On top of that, the CD games aren't region locked.
What you want, is a Duo R.
A Duo R with an Arcade Card can play everything except 5/6 SGX games that few people give a shit about and US HuCards. The only US HuCards you should care about would be the text heavy ones. There are only a small few text heavy US HuCards and you might not even care about those. Neutopia, Order of the Griffon, Neutopia 2, that's pretty much it. The majority of the games that were released in HuCard in both regions either have very little text, no text, or had English text even in their Japanese release.
Unless you are the collector type or have some weird nostalgia for shitty covers, you can pretty much just forget the TG-16 ever even happened. Its about as relevant as the Japanese version of the Atari Jaguar, or American versions of Renault automobiles.