According to the FDA, ibuprofen brand or generic, is supplied as a racemic mixture. Here's a quote from the FDA's prescribing information from Motrin suspension: "The active ingredient in MOTRIN is ibuprofen, which is a member of the propionic acid group of nonsteroidal antiinflammatory drugs (NSAIDs). Ibuprofen is a racemic mixture of [+]S- and [-]R-enantiomers."

and

"Pharmacokinetics - Ibuprofen is a racemic mixture of [-]R-and [+]S-isomers. In vivo and in vitro studies indicate that the [+]Sisomer is responsible for clinical activity. The [-]R-form, while thought to be pharmacologically inactive, is slowly and incompletely (~60%) interconverted into the active [+]S species in adults. The degree of interconversion in children is unknown, but is thought to be similar. The [-]R-isomer serves as a circulating reservoir to maintain levels of active drug."

Source: http://www.accessdata.fda.gov/drugsatfda_docs/label/2007/019842s020lbl.pdf

tl;dr: Brand and generic are the same