Here's why:
* Different Generations: Pokemon Ruby and Emerald are from the third generation of Pokemon games (Generation 3). They are not compatible with each other for wireless trading or battling.
* Wireless Compatibility: While the DS Lite has wireless capabilities, it's limited to games within the same generation. To play wirelessly, both players would need games from the same generation, like Pokemon Ruby and Sapphire or Pokemon Emerald and FireRed/LeafGreen.
To play together, you would need one of the following:
* Two games from the same generation: Both players need games like Ruby/Sapphire or Emerald/FireRed/LeafGreen.
* A later generation game: If one of you has a game from a later generation (like Diamond/Pearl or Black/White), you could trade Pokemon via the GTS (Global Trade System), which allows trading with players worldwide.
Let me know if you have other questions about Pokemon games!