There are a lot of great suggestions here already, so I will just share Mini Review with you as a discovery tool. I like to use them because they have a lot of filters to help you find a mobile game. For example, here's their list for free, single-player, offline games with no ads or in app purchases, sorted by highest user score. They also have an app for both Android and iOS with the same info and filtering as the site.
Have you tried Itch.io? They have a lot of Gameboy and NES roms that are "Name your own price." I don't have any recommendations - I've just started poking around with homebrew roms myself.
Warframe and Lotro are terminal illnesses for me. I'm never done playing them. It's an endless cycle of dressing up a hobbit in Middle Earth or dressing up a Warframe in space.
I don't mind DLC that's done right for games I love. I just know it's a common complaint for Paradox games to have a lot of DLC. That said, there are games that have produced a ton of free updates with very little DLC, like No Man's Sky, Terraria, Minecraft, etc. So, I don't know that it's always necessary to have a ton of DLC to support ongoing game development. It's all very subjective and varies a lot from game to game.