He served as captain, is the player with the most caps and is the all-time top scorer of the Guatemala national team.

At the age of 12, he joined the youth divisions of Club Social y Deportivo CSD Municipal, and at 16, he made his professional debut.

[5] He became a starter for Municipal and a young star in the Guatemalan league until 2000, when he traveled to Europe to play for a short time alongside compatriot Guillermo Ramírez at Greek club PAS Giannina.

Ruiz' overtime goal in extra time of MLS Cup 2002 gave Galaxy the title.

During the postseason in the conference semifinals, Ruiz scored two goals in the second leg match against the Colorado Rapids, but FC Dallas were eliminated on penalty kicks.

In February 2006, MLS fully bought Ruiz's contract rights from his former club, Municipal, and FC Dallas was able to negotiate a multi-year deal.

Following the conclusion of the 2007 season, Ruiz appeared to be unwilling to return to Dallas and to be holding out for a move back to the Galaxy.

On 31 January 2009, Ruiz signed a contract with Paraguayan club Olimpia Asunción under the request of then-coach Ever Hugo Almeida.

[15] Amongst Ruiz' most remembered goals, came in a 2–0 victory in the Paraguayan superclasico against Cerro Porteño and a free kick against 3 de Febrero.

[21] Since departing Olimpia, Ruiz became friends with Denis Caniza, Mario Jara and Juan Lucero and remained in contact with them.

[22] Ruiz signed with Puebla on 30 June 2009 under head coach José Luis Sánchez Solá.

He made his debut on 18 August 2010 in the playoff round of the Europa League against Austria Wien, becoming the first Guatemalan footballer ever to appear in a UEFA competition match.

[23] On 26 March he scored Philadelphia's winning goal in the home opener of the 2011 MLS season against the Vancouver Whitecaps FC.

[29] On 20 February 2013, DC United announced that the club had signed Ruiz via the MLS allocation process to a one-year deal.

He played his first international match on 11 November 1998, a friendly against Mexico, and scored his first goal against El Salvador at the 1999 UNCAF Nations Cup.

[33] After scoring eight goals in nine matches during the 2002 World Cup qualification campaign and already having a successful career in the MLS, Ruiz was the focal point of the Guatemalan team in qualifying for the 2006 FIFA World Cup, leading the team in scoring as they reached the final stage of the CONCACAF region.

[36] He then participated in the 2011 CONCACAF Gold Cup,[37] scoring one goal against Grenada in the first round and another one against Mexico in the quarterfinals in a 2–1 defeat.

On 16 October 2012, Ruiz again announced his retirement from international competition after a 3–1 loss to the United States at Livestrong Sporting Park, which eliminated Guatemala from 2014 World Cup qualification.

On 6 September 2016, Ruiz scored 5 goals against Saint Vincent and the Grenadines in his final farewell match for Guatemala.

This gave him a total of 39 goals in 47 qualifying games and made him the highest goalscorer of all-time, from any country, in FIFA World Cup qualification history.

Municipal Los Angeles Galaxy DC United FC Dallas Individual Ruiz is currently the 11th all-time leading goal scorer in MLS history.