Before the era of modern smartphones, the landscape-oriented resolution was the gold standard for high-end feature phones like the Nokia E71, E63, and Samsung Jack. These "landscape" screens provided a wider field of view, making them perfect for strategic simulations, racing, and cinematic platformers.
The best Java games for 320x240 were not just "mobile ports"; they were unique experiences tailored for short bursts of play (waiting for the bus) but with deep progression systems.
Search Google Scholar for:
Since the official mobile storefronts for these devices have largely closed, enthusiasts rely on archival sites and emulators: Java mobile games for 320x240 - Mobiles24