here's some things I can think of:
- New Game+ type stuff- I love beating a game and having the things I do actually matter for a future playthrough. This might be something like carrying over the stats of characters in Chrono Trigger so you can more easily get the different endings, or just something simple like getting a special item or two like in Metal Gear Solid.
- When games aren't too long- idk I just can't get into really long games anymore. Shorter games with lots of replayability are more what I like to see.
- Games with good art styles- not a big fan of the whole super realism thing and sadly games that do that look extremely dated after a while. Games that try their own kind of art style usually still look good years later.
- Sequels that try something new and different in a big way but still capture the feel of the previous games in the series. Metroid Prime and the Legend of Zelda: the Wind Waker are perfect examples of this.