People will be looking for Samsung to "really redesign and create an experience that feels less packed," Stofega said.
Samsung also has been updating phones by making their screens larger. The S4's display measures 5 inches diagonally, compared with 4.8 inches on the S III and 4 inches on the original S from 2010. The iPhone's screen has stayed steady at 4 inches since 2012.
Meanwhile, Sony Corp. said its new Xperia Z2 smartphone will have noise-cancelling technology that works with an in-ear headset sold separately. It will be able to capture video in the emerging 4K resolution, which offers four times the details as current high-definition video. Sony also announced a companion tablet and a cheaper, mid-range smartphone.
Nokia Corp. is targeting emerging markets with its Nokia X line of phones, starting at 89 euros ($122). It uses Google's Android operating system rather than the Windows Phone software from Microsoft, which is about to buy Nokia's handset business. But Nokia will replace many Google services on Android with Microsoft services and a Windows-like home screen.
Lenovo Group Ltd. announced three new smartphones, including the $269 glass-exterior S850 targeted at "fashion-conscious users." The other two phones promise longer battery life.
But even phones with spectacular features and designs might still go unnoticed if they aren't from Apple or Samsung.
"We've got really two companies that capture the lion's share of revenue and profit," Hays said. "There's lots of attention lavished on them because they have the most to lose."
AP Technology Writer Youkyung Lee in Seoul, South Korea, contributed to this story.