Setting aside any criticisms, wildly inappropriate jokes, or references in general to racial preferences in the real world, I'll concentrate on the fantasy reference in which you're asking this question. Since most of the fantasy I deal with lately involves D&D (most electronic RPGs I've played as of late seem to feature humans predominantly), I'll concentrate further on D&D standards for races.
I don't really have an overall favorite. Each has its own benefits and drawbacks. Since some are better suited to certain classes, I'll discuss that, briefly. Keep in mind that this is just my opinion.
Most fighters, barbarians, and paladins, as well as some rangers and monks, rely heavily on their physical prowess to add force to their blows. As such, a bonus to strength is helpful. Half-orcs and their ilk make great members of these classes, with the exception of the Paladin. Paladins require charisma, and therefore a race with a penalty to charisma is ill-suited to the path. That doesn't make a half-orc paladin impossible, just unlikely (and with the Paladin class already being rare, that makes half-orc paladins exceptionally so.) Dwarves have no direct strength bonus, but they do have a constitution bonus, which also helps fighting classes a great deal. Humans and half-elves make average fighters. The human can get an extra feat, which can speed up progression along one of the lines of fighting-based feats, and the human also gets an extra skill point per level, which makes up in part for the fighter's dearth of ability in that area. Among monstrous races, the Hobgoblin is a nice choice. They get bonuses to dexterity and constitution, and they get no ability score penalties. Though some players and DMs argue that this makes the Hobgoblin overbalanced, I don't think that is the case. Hobgoblins don't get anywhere near the number of abilities that most standard races do, such as an elf's immunity to sleep, a dwarf's stonecunning, and a human's extra feat and skills. Their ability score bonuses might be slightly overbalanced, but not exceptionally so. The worst races for strength-based fighters, obviously, are ones that generate a strength penalty: Gnomes and Halflings. They can fight, sure, but they're usually better off concentrating on dexterity.
Dexterity-based warriors; Archers:
Many rogues and bards, some fighters, monks, and rangers, and a small handful of Barbarians and Paladins rely on their manual acuity and surefootedness in combat rather than sheer power. Some use bows or other projectiles, while some use melee weapons. A cornerstone of this type of character, when using a melee weapon, is the Weapon Finesse feat, which allows Dexterity to be used in place of Strength as a modifier to attack rolls. Halflings and Elves get bonuses to dexterity, so make good choices for this type of fighter. Humans' bonuses remain useful, as stated above, and Hobgoblins' prowess in this field is perhaps even greater than as strength-warriors. No core race has an inherent penalty to dexterity, but gnomes and dwarves, with their lack of bonus combined with their slow base movement, usually find it slightly more difficult to pursue this path. The difference is not great, though; dwarf rogues can be very effective, and gnome rogues are almost as infamous as halflings in many parts. I play in a campaign where goblins are considered a PC race rather than a monstrous one, and they make excellent rogues as well. (+2 dex, -2 charisma)
Clerics, druids, and to a lesser extent, paladins and rangers, use their intuition and willpower to draw forth power from outside themselves. Wisdom is their most important statistic. Wisdom, however, is not a bonus for any core race. The Vanara, monkeylike people of the Oriental Adventures setting, have a wisdom bonus, and are tailor-made for the shaman class of that same setting, but if allowed to proceed as clerics or druids, would make excellent ones. Divine spellcasters tend to be decent at physical fighting, as well, and therefore races like the dwarf who get fighting bonuses make decent clerics. Elves make nice druids because they start play with free proficiency in bows, and as a druid they can cast ironwood spells to make arrows that use no metal but are just as sharp and deadly as arrows that do--thus proving effectiveness with a martial weapon uncommon to divine casters, without violating the druidic faith.
Wizards, sorcerers, and bards use their own power to form magical energies into the effects they desire. There's a bit of disagreement among many players about which races are best suited to the job. No core race has a bonus to intelligence or charisma, which wizards and sorcerers, respectively, need most. Dexterity is normally considered to be the second most useful skill, which fits in well for the stereotype of Elven wizards. However, constitution is also a very nice thing for an arcane caster to have--it helps make up for their lack of hit points, as well as assisting their concentration checks. Since elves have a constitution penalty, some players look to the halfling race when they consider an arcane caster--a concept which was impossible in second edition, and most people who favor traditional ways of thinking frown upon it. Those people frown even more upon another race that makes a good wizard in third edition: the dwarf. Yes, indeed, a dwarf has a bonus to the useful score of constitution, a penalty to charisma (which hurts sorcerers, but has little effect on wizards), and to top it off, gets a bonus to metalworking Craft skills that wizards often need to make magical items. Indeed, a dwarven wizard would be an interesting character, and no less powerful than an elf with the same level of experience. (The elf would have proficiency in a sword and bows, and that gets to be irrelevant quickly as a wizard concentrated less and less on fighting and more and more on magic.)
Now, keep in mind, the remarks I've made here are almost entirely related to the concept of playing an effective character. You can, of course, have any base race/class combination and make a good character: one who you enjoy roleplaying, especially. I've been tossing around the idea of an orcish, or perhaps even ogre wizard, though I'm not sure how big a problem an ogre's ECL would be. (I got the idea from Rubeus Hagrid.)
That help any?