Portable/Side GTAs never had the popularity or the longevity that the main titles have, but almost all portable GTAs were well received and loved by those who played it.
Ignoring the ports of the first 2 GTA games on the GBC, the first proper portable title we had was GTA Advance. It was almost a port of GTA 3 for Advance and it shows. In many ways it was almost like a bridge between the 2D and the 3D era of GTA. It was a fun little thing, but nothing really special.
GTA Liberty City Stories was a very popular hit for the PSP. It was a full, 3D GTA title on the go. It was basically III and VC melded in one game and is portable, and it proved really well and really popular. It became one of the selling points of the PSP (personally the reason I bought it). GTA Vice City Stories would follow about a year later with refined gameplay mechanics, optimization, and was executed much better than LCS. It also proved popular (though not as much)
GTA Chinatown Wars was released on the Nintendo DS and became one of the most popular games on the system. It had the aesthetics of the 2D era, gameplay of the 3D era, and the world of the HD era. It was a formula that was risky and new, but was ultimately great in the end. It also took advantage of the touch controls of the DS and the implementation was also well-received by players. CTW would be ported onto PSP with better graphics and added content, with the expense of the touch minigames, and to the mobile phones.
Then comes the next generation of portable gaming systems, the Nintendo 3DS and the Playstation Vita. However, Rockstar did not create another portable game for these systems. It's a shame. These systems are basically much improved and perfected versions of their predecessors. Portable GTAs had always been somewhat tie-ins to the game(s) in their era (LCS and VCS to the 3D era games and CTW to IV) and they probably wanted to put out a new game first to create a tie-in. However GTA V was still a few years away and IV was already a few years back. But Rockstar could've stuck to the formula of their previous games or create improved ports of previous games to the handheld systems. A CTW like game with better graphics and more content would've been really great and a 3D era style game or improved port of previous games for the Vita would've been awesome as well. GTA is a very popular video game IP and bringing GTA games to these systems would help the sale of these systems, especially the Vita which didn't sell as well as expected.
I think Rockstar is a fool not to continue and create full-fledged portable games. Sure, the mobile market has somewhat overtaken the portable gaming market, proven by it's popularity and the ports of III-LCS to mobile systems, but I think Portable gaming systems still have a major advantage to mobile systems, the controls, graphics, size. (which mobile systems are also catching up to) Portable developers have to find that sweet spot where it could work that the mobile systems can't. Rockstar games could also find or redo a new formula that works with the portable systems like they did with CTW.
With the release of the Nintendo Switch, a portable/couch system hybrid. I think Rockstar still has a chance to create something as unique as CTW. I personally would love a CTW styled game set on Vice City or Las Venturas. Maybe make it 3rd person but keep the gameplay and over the top-ness like CTW and the world of the HD era. Rockstar has proven that they have amazing talent in creating portable games (mainly Rockstar Leeds), so why not do it?
What do you guys think about a new portable/side GTA games? How do you think R* will do it? Will they ever even do it? With the current structure of Rockstar Games, the possibility of another portable game is slim.